REPORT. Establishment of a biogas grid and interaction between a biogas grid and a natural gas grid. Project Report January 2011

Transkript

1 Establishment of a biogas grid and interaction between a biogas grid and a natural gas grid. Project Report January 2011 REPORT Danish Gas Technology Centre Dr. Neergaards Vej 5B DK-2970 Hørsholm Tlf Fax

2 Establishment of a biogas grid and interaction between a biogas grid and a natural gas grid Torben Kvist Danish Gas Technology Centre Hørsholm 2011

3 Title : Establishment of a biogas grid and interaction between a biogas grid and a natural gas grid. Report Category : Project Report Author : Torben Kvist Date of issue : Copyright : Danish Gas Technology Centre File Number : ; h:\734\89 biogasnet\resumerapport\resumerapport_final.docx Project Name : Establishment of a biogas grid and interaction between a biogas grid and a natural gas grid ISBN :

4 DGC-report 1 Table of Contents Page 1 Introduction Background A biogas vision Examined subjects Overall energy review Biogas and the Danish energy system Value of storing biogas production Gas quality and measurement Experience with a biogas grid Application of biogas Sulphur removal Measurement Value of biogas for a CHP plant Converting natural gas fired engines to biogas Costs of conversions Gas quality requirements Design of the biogas grid system Alternative application of the biogas Ownership and liability Organization of Bioenergi Vest Required agreements Business models Applied economical key figures Assessment of Stage Assessment of Stage

5 DGC-report 2 Appendices Appendix 1: Overall energy review Appendix 2: Biogas and the Danish energy system Appendix 3: Gas quality and measurement Appendix 4: Value of biogas for a CHP plant Appendix 5: Converting natural gas fired engines to biogas Appendix 6: Establishment of the biogas grid Appendix 7: Ownership and liability Appendix 8: Business models

6 DGC-report 3 1 Introduction This report summarizes the investigations that have been conducted as a part of the ForskNG project Establishment of a biogas grid and interaction between a biogas grid and a natural gas grid. The report is based on the notes produced during the project. All notes are attached as appendices. For details and references please refer to the attached appendices. The following partners have participated in the project: HMN Naturgas I/S (Project responsible) Ringkøbing-Skjern Municipality Danish District Heating Association (Dansk Fjernvarme) Wärtsilä Danmark GE Jenbacher Rolls-Royce Marine 1 st mile Danish Gas Technology Centre (Project manager) The project was financially supported by Energinet.dk through the ForskNG programme.

7 DGC-report 4 2 Background 2.1 A biogas vision The Ringkøbing Skjern Municipality has a goal of producing renewable energy corresponding to the total energy consumption within the municipality in In 2007 the production of renewable energy contributed with 20 % of the total energy demand. The remaining 80 % shall be covered be various sources as Wind power Solar energy Energy savings in buildings and in transportation Various types of bioenergy This report focuses only on one type of bioenergy, namely biogas from manure and crops. The municipality made an assessment of the biogas potential within the municipality and it was found that The Biogas potential is 60 mio. m 3 CH 4 per year Degasification of manure contributes with 30 mio. m 3 CH 4 per year. It is assumed that 80 % of the manure in the municipality will be used for biogas production. Energy crops (maize) contribute with 30 mio. m 3 CH 4 per year Energy crops will cover 5 % of the farmland in the municipality. Energy crops can be stored, which will make the biogas production flexible allowing a high production in the winter when the heat demand is highest. The biogas can substitute 20 % of the total energy consumed in the municipality. The idea of the municipality was to establish a widely spread system for production of biogas consisting of decentralized and 1-3 centralized biogas plants. The municipality planned to establish a biogas grid for distribution of biogas to the natural-gas fired engine-based power plants in the

8 DGC-report 5 municipality. A sketch of the biogas system consisting of numerous biogas plants and a biogas grid is shown in Figure 1. Figure 1 Sketch of potential locations of biogas plants and biogas grid. Each dot represents a farm with animal production. The circles around the dots represent a cluster of farms delivering manure to one biogas plant.

9 DGC-report Examined subjects The biogas vision described by the municipality defined the framework of this project. Based on this framework the project examined different aspects relevant to the establishment of a biogas grid for distribution of biogas to local decentralized combined heat and power plants. The following subjects are treated in the report: Biogas production and demands Biogas in relation to the overall energy system Measurement in relation to billing the biogas production Value of biogas for local power plants Requirements for conversion of natural-gas fired engines to biogas Design of the biogas grid Ownership and liability Business analysis These subjects are treated separately and the results are given in the eight notes that are attached as appendices. Different partners of the project were responsible for the different notes. This report gives a brief summary of all the produced notes.

10 DGC-report 7 3 Overall energy review Decentralized CHP units cover the demand of heat in their respective areas of supply. This demand varies during the year and, therefore, also the fuel consumption. The average fuel demand was assessed as averaged actual natural gas consumption for the period HMN Naturgas contacted the CHP units, which might be supplied by biogas, for information on how much biogas they expected to acquire if a biogas grid were to be established. Expect for one unit all units were interested in using biogas if the price is right. In this case right means that the CHP plants can produce heat at a price that is not higher than today. Instead of converting existing natural-gas fired engines most plants intend to buy new dedicated biogas engines. Hereby they will obtain engines sizes that better match the heat demand in summer time than the existing natural-gas fired engines. This all means that the biogas engines will not be able to cover the whole heat demand during winter time. This is illustrated in Figure 2, where it is shown that the demand exceeds the production during the winter. Furthermore, the figure shows that production exceeds consumption in the summer period Månedsforbrug i NG-ækvi. m jan feb mar apr maj jun jul aug sep okt nov dec Gns. gasforbrug Biogasproduktion Forventet biogasforbrug Figure 2 Average present natural gas consumption, expected biogas consumption as well as expected biogas production The surplus of biogas during summer time, represented by the area confined by the brown and the blue curve in Figure 2, can be upgraded to natural gas quality and distributed by the natural gas grid. If the whole surplus should be upgraded an upgrading capacity corresponding to m 3 biogas per hour would be required. The costs related to the upgrading would be 17 mio.

11 DGC-report 8 DKK per year or 0,19 DKK per m 3 of biogas produced. See Table 1. For prices of upgrading please refer to Appendix 1. Table 1 Number of equivalent full-load hours and upgrading cost related to biogas that cannot be used by CHP for production; expected gas consumption and gas production are as shown in Figure 2. Eqv. full load hours H Upgrading costs DKK/m 3 CH 4 1,52 Upgrading costs Mio. DKK/year 17,0 Upgrading costs DKK./m 3 biogas prod. 0,19 The data given in Table 1 is based on the expected gas consumption and gas production as shown in Figure 2. This will of course change if these conditions are different than expected. If the biogas production is lower than expected, less biogas needs to be upgraded. To some extent it will be possible to vary the biogas production during the year. This will also reduce the need for upgrading and, in turn, the related costs. If the biogas production can be varied to make the surplus of biogas production constant, the specific upgrading costs would be 8,2 mio. DKK corresponding to 0,90 DKK/m 3 CH 4. If the total heat demand in summer is reduced, for instance due to installation of large solar heating units, the picture would be the opposite. Then more biogas must be upgraded leading to higher upgrading cost. For further details, please refer to Appendix 1.

12 DGC-report 9 4 Biogas and the Danish energy system With a system like the one suggested, upgraded biogas will be fed to the natural gas grid during the summer period when the natural gas consumption is lowest and in the winter period when the natural gas consumption is highest the biogas grid needs back-up from the natural gas system. The service is important to take into account if socio-economic aspects are considered. Therefore, a rough analysis of the whole chain from transport of natural gas from the North Sea to shore, transmission, storage and distribution and how biogas fits into this system was conducted. It was found that biogas will only affect the existing gas system marginally. If a biogas engine-based CHP plant sells the electricity production at fixed prices there will be no motivation for adjusting the power production according to the need for electricity. This means that Energinet.dk, as the balancing-responsible, must pay others to deliver the required system service because a biogas unit produces power independently of the actual demand. In this section, the value of electricity production that depends on the actual price and thereby the demand for electricity will be described. This is done by comparing the average electricity price at Nordpool with a power weighted average price (Nordpool is a market place for trade with electricity). The simple average price corresponds to the value of constant electricity production. The power weighted average price expresses the value of production that depends on the market price. This means that the difference between the two is the additional value of price dependent electricity production compared to constant production. The basis for the analysis is the decentralized electricity production sold at market conditions in the eastern and the western part of Denmark. From the homepage of Energinet.dk it is possible to find historical data for the electricity prices. From these data the simple average and power weighted electricity prices for one year periods were calculated and are given in Table 2. For the period the price dependent electricity production had a value that was DKK/MWh higher than the value of a constant electricity production.

13 DGC-report 10 Table 2 Average market price of electricity (DKK/MWh) as well as difference between simple and power weighted average price for West and East Denmark West Denmark East Denmark Year Simple Weighted Difference Simple Weighted Difference average average average average ,39 282,56 41,17 245,93 273,94 28, ,70 435,55 14,84 422,28 429,55 7, ,43 289,02 20,59 296,90 319,69 22, ,29 336,98 26,69 321,81 341,27 19,46 The numbers in Table 2 were calculated from total decentralized electricity production in Denmark. This means that the data covers both production from natural-gas fired engines and turbines, where the production depends on market price of electricity and production from for instance household waste, which takes place independently of market price. It was found that around half of the decentralized electricity production sold on Nordpool takes place independently of the electricity price. This will influence the calculated additional value of price sensitive electricity production compared to constant production. If these 50 % of base load are omitted from the analysis, the additional value of price-flexible power production would be DKK/MWh instead of DKK/MWh as shown in Table Value of storing biogas production It is not practically possible to store biogas production for longer periods. It is, however, possible to store it for some hours. This means that it will be possible to avoid electricity production during night time when the electricity prices typically are lowest. A gas storage with a capacity of six hours of production means that it would be possible to avoid production from midnight to six in the morning. That could increase the average value of the electricity production by DKK/MWh. A gas storage with a capacity of 12 hours of biogas production would avoid electricity production from 8 pm to 8 am. That would increase the average value of the electricity production by DKK/MWh.

14 DGC-report 11 The present analysis regarding electricity values is only valid as long as the electricity production based on biogas does not affect the prices on the electricity market. As biogas contributes with less than 4 % of the total decentralized power production, it is not likely that a change in production profile of biogas-fired CHP plants will affect the prices significantly. For further information please refer to Appendix 2.

15 DGC-report 12 5 Gas quality and measurement Different issues regarding gas quality and measurements must be addressed as regards a system with a number of biogas producers connected to a number of consumers by a gas grid. Manure based biogas has a relatively high content of H 2 S, typically between 1000 and 4000 ppm in raw biogas. H 2 S both smells and is very corrosive. As the biogas leaves the biogas reactor it has a relatively high temperature (37-52 C) and it is saturated with water vapor. This leads to formation of an acid condensate as the temperature decreases. All components in the gas system, which are not made from plastic based materials or stainless steel, might corrode. Furthermore, the high moisture and sulphur content of biogas means that it is not simple to measure the amount of biogas produced or consumed Experience with a biogas grid From 1990 to 2005 around 60 private households were supplied from a biogas grid in Revninge on Funen. After this period the grid, the meters and the supplied boilers were examined. It was found that the biogas had made no harm to the biogas grid, but boilers and meters were damaged due to corrosion Application of biogas Biogas can be applied in different ways. Today, the most common ways are as fuel for gas engines and upgrading to natural gas quality. During upgrading the CO 2 content of the biogas is removed in order to increase methane concentration and thereby the heating value of the gas. Manufacturers of modern high-efficient gas boilers for households were contacted and it was found that these boilers are not suited for biogas due to low and varying heating value and density of biogas. In Denmark, practically the whole biogas production is used for combustion engines without being upgraded. This technology allows high efficiencies and it has the advantage that the engines are only slightly sensitive to variations in gas quality. The biogas can be applied as fuel for existing natural-

16 DGC-report 13 gas fired engines at CHP plants. For information on costs related to conversion of existing natural-gas fired engines to biogas operation as well as gas quality requirements etc., please refer to Section 7 and Appendix 5. Most gas turbines for gaseous fuels are developed for natural gas. If changing from natural gas to biogas operation, substantial modifications of both compressor and turbine are required. Furthermore, gas turbines are much more sensitive to variations in gas quality than gas engines. Therefore, gas turbine units are not foreseen as biogas consumers in the Ringkøbing-Skjern Municipality Sulphur removal In Denmark the most common technology for sulphur removal from biogas is application of biological filters. In these filters the H 2 S is converted to solid sulphur or H 2 SO 4 by use of oxygen. The reactions are given below. H 2 S +½ O 2 H 2 O + S S + H 2 O + 1,5 O 2 H 2 SO 4 Normally, 5 % of air is added to the biogas in order to supply the required amount of oxygen for sulphur removal. However, this is problematic if, subsequently, the biogas is supposed to be upgraded to natural gas quality, since the nitrogen content in the air makes it impossible to fulfil the requirements to natural gas. However, it is possible to add lower amounts of air or add pure oxygen instead of air for the sulphur removal. The main advantage of biological sulphur removal is that it is a relative cheap method for larger gas flows. Other methods are more relevant for smaller gas flows. Some of these are described in Appendix 3 together with prices of the sulphur removal. As mentioned earlier, experiences from Revninge show that the gas grid is not harmed by the presence of sulphur. This means that it should be possible to do the gas cleaning at the consumers instead of by the producers. This allows few and large units instead of several smaller units and thereby lower sulphur removal cost. However, the approach is likely to result in an in-

17 DGC-report 14 crease in maintenance costs related to fittings, compressors and other equipment due to the higher sulphur content. For further information please refer to Appendix Measurement In order to determine the amount of biogas produced with a sufficient accuracy it is necessary to choose a system that can handle the challenges related to biogas. Among the conditions that must be considered before choosing measurement system are: - Moisture content - Range of measurement - Risk of pulsations - Required accuracy There are a number of different technologies available for measurement of gaseous flows. Some of them are described in Appendix 3 together with their respective characteristics. Based on information from suppliers a measurement system for 100 m 3 /h of biogas can be acquired for around DKK. This price is based on a turbine wheel meter and IR sensors determining the O 2 and CH 4. If a higher accuracy is required a gas chromatograph can be chosen instead of an IR sensor. The yearly maintenance costs are assessed to be around 20 % of the investment. For further details please refer to Appendix 3.

18 DGC-report 15 6 Value of biogas for a CHP plant The many engine-based natural-gas fired local CHP units in Denmark can be converted to biogas operation. However, a conversion from natural gas to biogas requires that the CHP plant can provide their customers with heat at a price that is not higher than the present price using natural gas. Today, most natural-gas fired CHP plants are acting on the free electricity market. This means that they produce electricity and heat on the engines when the electricity price is high, and heat on boilers when the electricity price is low. This way of operation has to be reconsidered if changing to biogas. Furthermore, the conversion implies investments (see next section or Appendix 5). These issues set an upper limit for the value of biogas for a CHP plant. This value has been determined for two CHP plants in the municipality - Ringkøbing and Spjald Kraftvarmeværk, respectively. The analysis is based on historical electricity prices (year 2008 and 2009) and on case simulations using the computer program EnergyPro. In order to assess the value of biogas for the CHP plants different scenarios were defined and analysed through model calculations. The chosen scenarios were: 1. Base case: natural gas operation and conditions as in 2008 and Biogas as base load and fixed electricity prices. 3. Biogas as base load and market dependent electricity prices. 4. Biogas corresponding to 150 % of base load and fixed electricity prices. 5. Biogas corresponding to 150 % of base load and market dependent electricity prices. Scenario 1 is used for determining the price of heat, which should be matched by biogas operation. The calculations have shown values of biogas for CHP plants varying from around 3,9 to 4,5 DKK per m 3 of natural gas equivalent. This corresponds to 2,3 to 2,7 DKK per m 3 of biogas (65 % methane). The highest values were found for Ringkøbing in See Table 3.

19 DGC-report 16 Furthermore, the analysis showed that the operation strategy covered by scenario 3 - biogas consumption corresponding to 150 % of base load and fixed electricity prices - generally gives the highest and most stable values of biogas. Table 3 Calculated values of biogas for the CHP plants in Ringkøbing and Spjald with the electricity prices for 2008 and Unit is DKK/m 3 (n) natural gas equivalent. Ringkøbing Spjald 2008, price of heat: 326 DKK/MWh 2009, price of heat: 187 DKK/MWh 2008, price of heat: 275 DKK/MWh 2009, price of heat: 136 DKK/MWh Scenario 2 4,19 3,86 3,87 3,48 Scenario 3 4,42 3,27 4,15 3,64 Scenario 4 4,43 4,12 4,03 4,12 Scenario 5 4,03 3,94 4,65 2,38 According to the rules for taxes and subsidies valid for 2010 the prices could be increased by 0,33 DKK pr. m 3 of natural gas equivalent compared to the values given in Table 3. For further details please refer to Appendix 4.

20 DGC-report 17 7 Converting natural gas fired engines to biogas Practically all larger natural gas fired engines on CHP plants are turbocharged lean-burn engines. This allows high power, high efficiency and low NO x emissions. These engines can be modified for biogas operation. The required modifications vary, however, significantly for different engine types and models. This high content of CO 2 in the biogas means that the heating value of the biogas is only around 60 % of the heating value of natural gas. This means that the gas consumption will be 70 % higher for biogas (by volume) compared to natural gas if the power production should be kept constant. Besides CH 4 and CO 2, the biogas contains impurities as ammonia and H 2 S that can be harmful to gas installations. In this project three different engine manufacturers are represented. They are GE Jenbacher, Rolls Royce and Wärtsilä. They have supplied the project with information on required gas quality, necessary modifications and related prices Costs of conversions The different engines are fuelled differently. For the Rolls Royce and the Wärtsilä engines the fuel is supplied downstream from the turbocharger. On Jenbacher engines the fuel is supplied before the turbocharger. This means that in order to overcome the pressure after turbocharging the biogas must be pressurized to around 4 bar. That is not the case for Jenbacher engines. An engine with a 2 MW e power production thus requires a compressor at a price of 2-2,5 million DKK. The power consumption for biogas compression corresponds to 5 % of the total power production. Including operation, maintenance and depreciation costs this corresponds to around 0,06 DDK/kWh of electricity produced. In case of insufficient biogas production the engine must be able to operate on either pure natural gas or a mixture of natural gas and biogas. A conversion from natural gas to biogas operation requires a number of different modifications. The required modifications depend on engine type, model and age.

21 DGC-report 18 Among the possible required modifications are: Modification/change of control system Gas ramp for biogas Modified gas ramp for natural gas New or modified turbocharger Compressor for boosting the biogas pressure The engine suppliers have assessed the necessary modifications and the related cost for different engine models. The costs related to conversion of the engines vary from around DKK to DKK depending on engine model, size and age. Possible costs for biogas boosters are not included. Furthermore, if the H 2 S content in the biogas is not sufficiently low additional service cost must be expected Gas quality requirements Rolls Royce and GE Jenbacher have defined requirements regarding gas quality. Some of these are given in Table 4. Table 4 Requirements to biogas quality given by engine manufactures Rolls-Royce GE Jenbacher Lowest heat value 18 - [MJ/m 3 (n)] Gas temperature C 0 40 C Moisture Dew point: 5 80 % relative 4,3 bar Max. particle size 5 µm 3 µm Max. sulphur 1520 mg/m mg/m 3 1 Max. ammonia 50 mg/m 3 32 mg/m 3 Max. halogens 100 mg/m 3 65 mg/m 3 1 (Cl + 2 x Fl) 1 Valid for engines that are not equipped with catalysts. If the engines are equipped with CO or formaldehyde catalysts the concentration of sulphur and halogens are lower than given in Table 4. The engine suppliers expect the electrical efficiency to decrease by around 1 % point by conversion from natural gas to biogas operation. Depending on the H 2 S concentration in the fuel it might be necessary to increase the flue gas temperature in order to avoid corrosion of heat exchangers. Jenbacher recommends to increase the temperature after heat exchanger from around 60 C (which is normal for natural gas operation) to 180 C if the H 2 S con-

22 DGC-report 19 tent in the biogas is above 130 mg/m 3. This will decrease the heat production by % depending on exhaust gas temperature. For further details, please refer to Appendix 5.

23 DGC-report 20 8 Design of the biogas grid system This section will describe design of the grid for distributing biogas from the biogas plants to the decentralized natural gas engine based CHP plant in the municipality. The grid is planned to be a low pressure grid (1,3 bar (g)) made from PE-100 SDR17 pipes. The grid will be designed so a supply pressure of 0,3 bar(g) will available at all CHP plants. The biogas sources are evenly distributed all over the municipality but plant that is going to use the biogas are mainly in the northern part of the municipality. This means that a larger transport capacity from south to north is required. In order to design the biogas grid all relevant CHP plants in the municipality were interviewed. Based these interviews the required design data for the consumers were defined. See Table 5. Table 5 Plant Design data for the biogas grid Biogas consumption [m 3 (n)/year] Necessary input power [MW] Required amount of biogas [m 3 (n) biogas/h] Tim KV ,8 430 Videbæk KV , Troldhede KV ,2 338 Skjern KV , Lem KV ,4 986 Ringkøbing KV , Spjald KV , Hvide Sande KV , Kloster KV ,8 277 Ådum KV ,8 277 With these design data a biogas grid was designed. The result is shown in Figure 3.

24 DGC-report 21 Figure 3 Design of the biogas grid connecting the biogas producers with the CHP plants and the natural gas grid As shown in the figure it was chosen to include two grid compressors in the system. This allows for reduced diameters of the pipes. The savings due to reduced pipe dimensions can remunerate the investment and the operation of the two compressor stations. The investment costs of the system shown in Figure 3 would be: Main grid: 131 mio. DKK Grid at end users: 50 mio. DKK Grid compressors: 5 mio. DKK Upgrading units: 45 mio. DKK Conversions at CHPs 116 mio. DKK 1 Total: 347 mio. DKK excl. VAT 1 includes modification of existing engines and installation of new engines

25 DGC-report Alternative application of the biogas HMN Naturgas I/S examined the possibilities of upgrading and injecting the entire biogas production into the natural gas grid. It turned out that the 40 bar distribution grid in the municipality has sufficiently high capacity to take the entire biogas production. This solution means that the biogas grid can be established in smaller dimensions and, in addition, parts of the grid can be omitted. Upgrading all biogas also means that the modifications at the CHP plants including conversion and replacement of gas engines will be superfluous, as they will be supplied as they are today. The result will be significantly lower investments costs. Instead of 347 mio. DKK, as shown above, the required investment will be 255 mio. DKK - including upgrading units. However, operation of the upgrading plants will lead to significantly higher operation and maintenance costs. The feasibility of the two solutions is described in Section 10. For further information on grid design please refer to Appendix 8.

26 DGC-report 23 9 Ownership and liability The municipality of Ringkøbing Skjern has established a company called Bioenergi Vest (abbreviated BeV) to develop and promote the biogas vision. Beside the municipality, the local trade council and the agricultural organisation are involved in BeV. This section describes BeV s view on a possible organizational framework. One of the purposes of BeV is to ensure a framework for the establishment of the biogas plants. This includes obtaining the required financing as well as distributing and trading the biogas Organization of Bioenergi Vest Due to the hard financial situation for farmers today the idea is that BeV will be the owner of the biogas plants and a farmer or a group of farmer will lease the biogas plant from BeV. Both if it is a single farmer or a group of farmers who jointly leases a biogas plant, it is suggested that a biogas operation company is formed. This biogas operation company will lease the biogas plant, receive payment for the gas production and be responsible for operation of the plant. The leasing model is only one solution. Privately owned biogas plants can produce and deliver biogas at the same conditions as the leased plants. Within BeV it is planned to establish different companies. Each of these companies will cover different areas from gas production, distribution to trade of gas and will 100 % owned by the BeV mother company. BeV leasing will be the owner of the biogas plants and, therefore, be responsible of ensuring the required financing for biogas plants. Such a company will be subject to Varmeforsyningsloven (Heat Supply Act), which means that it will not be allowed to generate a profit. Furthermore, a commercial company will be established to be responsible for service and maintenance of the biogas plants, optimizing the operation etc. As owning and operating a biogas grid are covered by Varmeforsyningsloven it is not allowed to generate a profit from these activities. Therefore, it is unlikely that a commercial partner will be interested in this activity. Furthermore, the Danish natural gas distribution companies are not allowed

27 DGC-report 24 to own and operate biogas grids. Therefore, BeV will establish a company for setting up, owning and operating the biogas grid. Within BeV a commercial company to handle the trade of biogas will be set up. The company will buy the biogas from the biogas operation companies and sell it to local CHP plants and to another company that will upgrade the biogas to be distributed via the natural gas grid. The gas trading company will act in a market with other commercial entities Required agreements Responsibilities as well as financial relationships must be defined in a way to satisfy all individual partners as well as to encourage all partners to act optimally in relation to the entire system. In order to make such a system work as smoothly as possible a number of agreements between the different entities must be made. Some of these agreements are as follows. Agreement between the BeV leasing company and the biogas operation company about leasing of biogas plants. Agreement between the BeV trading company and the biogas operation company and gas consumers about gas trade. As the gas requirements of the CHP plants involve substantial seasonal fluctuations these agreements could include seasonal depending gas prices in order to match to match the biogas production and the local heat demand. Agreement between the BeV operation company and the biogas service company about service and maintenance of the biogas plant. Agreement between biogas producers and the BeV grid company regarding gas quality. The different gas consumers have different requirements. Therefore, it is suggested that the biogas quality should not satisfy all costumers. Final gas cleaning can take place at the consumers. For further information, please refer to Appendix 7.

28 DGC-report Business models The Ringkøbing-Skjern Municipality plans a staged implementation of their biogas vision. First stage involves establishment of five biogas plants, which will be connected to the CHP plant in Skjern. Second stage involves an expansion of the first stage to a grid that connects the 11 CHP plants mentioned earlier with around 60 biogas plants and a total methane production of 60 million m 3. This corresponds to the base case described in Section 3. The staged approach has a number of advantages. One is that a successful implementation of the overall biogas vision requires huge investments. A first stage can be used for convincing investors of the viability of the vision. This will require well-operating demonstration plants with high gas yields. A first stage can also be used for revealing technical and organizational challenges that must be handled before implementation of a second stage Applied economical key figures Biogas grid: Average price is DKK per km. Value of biogas for CHP plans: 4,12 DDK/ m 3 of methane. The value varies significantly and depends on prices of natural gas, required engine modifications in order to be able to run on biogas, how electricity is sold etc. (See Appendix 4). Value of biogas upgraded to natural gas quality: 4,83 DKK per m 3 of methane. Furthermore, investments cost of biogas plant, operational costs have been assessed Assessment of Stage 1 Stage 1 involves: 5 biogas plants 5 mio. m 3 of methane 1 power plant 35 km of gas grid

29 DGC-report 26 The minimum gas requirement of the CHP plant exceeds the biogas production of the five biogas plants. This means that there is no surplus of biogas and, therefore, biogas upgrading is not necessary. In order to establish and operate a biogas gas system that can handle and distribute biogas from the biogas plants the CHP plant BeV must charge 0,68 DKK/m 3 of methane. This means that the price of the biogas paid to the biogas plants is expected to be 3,44 DKK/m 3 of methane. This price must cover leasing expenses, manure handling, energy crops, operation and maintenance etc Assessment of Stage 2 Stage 2 involves: 60 biogas plants 60 mio. m 3 of methane 11 power plant 120 km of gas grid 2 gas compressors 2 upgrading units For assessment of stage 2 three different business cases were examined. Case 2A: 48 mio. m 3 of biogas production is used at CHP plants for heat and power production. This corresponds to the heat demand that is expected to be covered by biogas at the CHP plant. The remaining gas is upgraded to natural gas quality and distributed via the natural gas grid. Case 2B: The entire biogas production is upgraded to natural gas quality and distributed via the natural gas grid. Case 2C: 48 mio. m 3 of biogas production is used at CHP plants for heat and power production. The remaining gas production will also be used at the CHP plants, but for power production only. The heat will be cooled away.

30 DGC-report 27 Financial key figures for the three business models 2A, 2B and 2C: Model 2A o Farmers income from gas sale: 177 mio. DKK/year. o Simple payback period: 12 years. o Required transport fee to BeV: 0,36 DKK/m 3 CH 4 (or 22 mio. DKK/year). Model 2B o Farmers income from gas sale: 190 mio. DKK/year. o Simple payback period: 12 years. o Required transport fee to BeV: 0,85 DKK/m 3 CH 4 (or 51 mio. DKK/year). Model 2C o Farmers income from gas sale: 160 mio. DKK/year. o Simple payback period: 12 years. o Required transport fee to BeV: 0,19 DKK/m 3 CH 4 (or 11 mio. DKK/year). The required transport fee gives an account in balance. With the requisites given earlier it is shown that Model 2B will result in the highest income from gas sale to the farmers, where the entire biogas production is upgraded and sold as natural gas despite the significantly higher required transmission. For further information and assessment of the sensitivity on the results of the requisites made, please refer to Appendix 8.

31 Appendix 1 Produktion og afsætning Written by DGC

32

33 1 Biogasnettet i Ringkøbing-Skjern Kommune Produktion og afsætning Torben Kvist November 2010 Dansk Gasteknisk Center a/s Hørsholm 2010

34 2 Indholdsfortegnelse Side 1 Indledning Produktionspotentiale Biogas og gasapparater Villakedler Gasturbiner Gasmotorer Afsætning til kraftvarmeværker Biogas og naturgasnettet Opgradering af biogas til naturgaskvalitet Opgraderingsteknologier Opgraderingspriser Sæsonvarieret biogasproduktion Betydning af biogasmængde Følsomhed overfor anden vedvarende energi Solvarme Geotermi Biomasse Referencer... 24

35 3 1 Indledning I Danmark er der stor fokus på øget produktion og anvendelse af biogas. Formålet med dette notat er at undersøge hvordan forholdet er mellem forventet biogasproduktion og varmegrundlaget i Ringkøbing Skjern Kommune og undersøge i hvilken grad det er muligt at anvende naturgasnettet til at udbalancere et misforhold mellem biogasproduktion og varmebehov. MERE Nærværende notat er en del af afrapporteringen af arbejdspakke 1 for projektet Frame work for interaction between biogas and natural gas grids. Formålet med projektet er at undersøge mulighederne for etablering af et biogasnet, til forsyning af en række større gasforbrugere, der i dag forsynes med naturgas. Notat er skrevet af DGC. HMN har leveret data omkring gasforbrug og varmegrundlag. Projektet er økonomisk støttet af Energinet.dk via ForskNG programmet.

36 4 2 Produktionspotentiale Rinkøbing Skjern Kommune forventer biogaspotentialet svarer til en produktion på 60 mio. m 3 metan pr. år. Af dette vil halvdelen kunne komme fra gylle og halvdelen fra anden biomasse som energiafgrøder. 3 Biogas og gasapparater Villakedler I 2009 afsluttedes et projekt omkring nedgradering af gaskvaliteten i et naturgasnet fra naturgaskvalitet til biogaskvalitet. I den forbindelse blev muligheden for at anvende biogas i stedet for naturgas i bl.a. villakedler vurderet [1]. De seks største kedelbrænderleverandører blev forespurgt om deres vurdering af mulighederne for at tilpasse deres anlæg til biogas. Størstedelen af installationerne vurderes ud fra en ren teknisk betragtning, at være uegnet til anvendelse med biogas. Ingen af installationerne er godkendt til biogas. Endvidere vil det ikke være muligt at udskifte gamle kedler med nye. Bygningsreglementet kræver ved nyinstallation kondenserende kedler, som ikke findes på markedet til biogas. Det er derfor valgt at se bort fra villainstallationer som aftager af biogas Gasturbiner I området, der kan forsynes med biogas fra det planlagte biogas i Ringkøbing-Skjern Kommune er der flere gasturbiner, der i dag kører på naturgas. Gasturbiner er betydelige mere følsomme overfor variationer i gaskvalitet end gasmotorer. Siemens er blevet kontaktet og det er vurderet deres turbiner ikke egner sig til biogas med varierende gaskvalitet. Det er derfor valgt at se bort fra turbineanlæg som aftager af biogas Gasmotorer I området, der planlægges forsynet med biogas, er der en række decentrale kraftvarmeværker med naturgasfyrede motorer. Disse kan konverteres til biogasdrift. For mere information om konvertering af naturgasmotor til biogas refereres til Appendix 5.

37 I Tabel 1 angivet en liste med hvilke motormodeller der er og på hvilke kraftvarmeværker de er installeret. I visse tilfælde vil man formentlig vælge at installere nye motorer, der dedikeres til biogasdrift i stedet for at konvertere eksisterende motorer til biogasdrift. Tabel 1. Eksisterende naturgas fyrede gasmotoranlæg, der kan forsynes fra det planlagte biogasnet. 5 Værk Type Model Spjald KVV Motor Rolls Royce KVGS-18G4 Troldhede FVV Motor Caterpillar G3500 Videbæk Energifor. Motor Niigata 18V26HX-6 Motor WärtsiläCW220_S6_18V Motor JenbacherJMS620GSNLCE12 Ringkøbing FVV Motor Wärtsilä 20V24S6 Tim FVV Motor Caterpillar G3500 Lem FVV Motor Caterpillar G3616 Ådum KVV Motor Jenbacher JMS316GSNLC Kloster KVV Motor Jenbacher JMS300 Hvide Sande FVV Motor Caterpillar G3616 Motor Caterpillar G3616 Ørnhøj - Grønbjerg KVV Motor Caterpillar G Afsætning til kraftvarmeværker Decentrale kraftvarmeværker skal dække varmebehovet, der svinger henover året, i deres respektive forsyningsområder. Derfor svinger brændselsforbruget også hen over året. Baseret på det faktiske naturgasforbrug de seneste fem år for de i værker, der angivet i Tabel 1, er den mængde biogas, der potentielt kan afsættes til kraftvarmeværker blevet vurderet. Som eksempel på naturgasforbruget på et kraftvarmeværk, er naturgasforbruget for de seneste 5 år for Spjald kraftvarmeværk, angivet i Figur 1. Forbrugsprofilet for de øvrige kraftvarmeværker i området svarer til det viste.

38 Naturgasforbrug / m jan feb mar apr maj jun jul aug sep okt nov dec Figur 1. Naturgasforbruget for Spjald Kraftvarmeværk for årene Det samlede naturgasforbruget for alle de 11 anlæg, der vil kunne forsynes med gas fra det planlagte biogasnet er vist i Figur 2. I figuren ses middelforbruget for årene , sammen med minimums- og maksimumsforbruget i samme periode Månedsforbrug i NG-ækvi. m jan feb mar apr maj jun jul aug sep okt nov dec Gennemsnit min. værdi Max værdi Figur 2. Hhv. gennemsnits, minimum og maksimalforbruget for årene for de kraftvarmeværker, der kan forsynes med biogas fra det planlagte biogasnet.

39 7 5 Biogas og naturgasnettet HMN naturgas har kontaktet de kraftvarmeværker, der kan forsynes med biogas fra biogasnettet for at høre deres planer om konvertering fra naturgas til biogas, hvis der etableres et biogasnet. Bortset fra et enkelt værk har alle svaret at de var interesseret i at modtage biogas. En række af de forespurgte anlæg, har svaret at de overvejer at installere nye biogasmotorer i stedet for at konvertere de eksisterende naturgasmotorer. Der vil i givet fald blive installeret motorer, der er mindre end de eksisterende naturgasmotorer. Herved fås nogle biogasmotorer, der i størrelse bedre svarer til varmebehovet om sommeren. Når biogasmotorer ikke kan levere den nødvendige varme, vil den resterende varme blive produceret på de eksisterende naturgasfyrede motorer eller vha. af kedler afhængigt af markedsprisen for el. Det betyder at aftaget af biogas i vinterperioden vil være lavere end det potentiale der er vist i Figur 2. På baggrund af interviewundersøgelsen har HMN naturgas beregnet hvor stor en mængde biogas de decentrale kraftvarmeværker forventes at ville aftage. Det er vist i Figur 3 sammen potentialet for afsætning af gas til motorbaserede naturgasfyrede værker og den forventede biogasproduktion. Af figuren fremgår det desuden at den forventede biogasproduktion er større end det forventede biogasforbrug i perioden fra april til oktober. Det betyder at der skal findes en alternativ løsning. En mulig løsning er at opgradere den overskydende biogas til naturgaskvalitet og afsætte den via naturgasnettet.

40 8 Månedsforbrug i NG-ækvi. m jan feb mar apr maj jun jul aug sep okt nov dec Gns. gasforbrug Biogasproduktion Forventet biogasforbrug Figur 3. Biogasproduktion og biogasforbrug på kraftvarmeværker forbundet til biogasnettet. 5.1 Opgradering af biogas til naturgaskvalitet For at biogas kan afsættes til naturgasnettet kræves gassen renses og CO 2 indholdet skal fjernes (kaldet opgradering). Der findes en række forskellige teknologier til opgradering af biogas. I nedenståede beskrives de tre mest konventionelle opgraderingsteknologier, nemlig PSA anlæg, vandskrubberanlæg og aminskrubberanlæg Opgraderingsteknologier PSA står for Pressure Swing Adsorption. Det er et meget sigende navn for denne teknologi. I PSA anlæg separeres CO 2 fra metan ved adsorption på et fast materialer, typisk aktivt kul under tryk. Et PSA anlæg består af en række, typisk 4-6, parallelle beholdere med adsorptionsmateriale. Hver beholder arbejde i fire forskellige faser, adsorption, tryksænkning, regenerering og trykøgning. Under adsorption føres den komprimerede biogas ind gennem beholderens bund. Mens gassen ledes op gennem beholderen adsorberes CO 2 på overfladen af adsorptionsmaterialet. Gassen, der passerer adsorptionsmaterialet, indeholder omkring 97 % metan. Når adsorptionsmaterialet er ved at være mættet med CO 2, ledes den ikke-opgraderede biogas til en beholder med regenereret adsorptionsmateriale. Beholderen med det mættede

41 9 adsorptionsmateriale regenereres, hvilket sker ved at trykket i beholderen sænkes trinvist. I Vandskrubberanlæg udnyttes at CO 2 og metan har forskellig opløselighed i vand, og at opløseligheden stiger ved stigende tryk. Processen fungerer ved at komprimeret biogas ledes ind i bunden af en skrubber eller vasketårn, hvor den kommer i kontakt med vand, der ledes ind i toppen at skrubberen. Skrubberen indeholder fyldelegemer, der sikrer god fysisk kontakt mellem gas og vand. Ud af skrubberen kommer renset gas. Foruden CO 2 indeholder vaskevandet en del opløst metan. For at genindvinde denne metan sænkes trykket i en flashtank. Her udnyttes det, at metan lettere desorberes end CO 2. Den desorberede metanholdige gas fra flashtanken føres tilbage til den rå biogas. Vandet fra flashtanken ledes herefter over i stripperen, der ligesom skrubberen indeholder fyldelegemer. Heri strømmer vandet i modstrøm med luft, hvorved den opløste CO 2 desorberes fra vandet og følger med luften ud af stripperen. Aminvaskeanlæg minder en del om trykvandsanlæg. I begge tilfælde bringes biogassen i fysisk kontakt med en væske i en skrubber, hvor CO 2 går fra gasfasen og over i den modstrømmende væske og følger denne ud af skrubberen, og renset biogas kommer ud gennem toppen af skrubberen I modsætning til trykvandsanlæg, hvor CO 2 opløses i vandet, sker der i skrubberen på aminvaskeanlæg en egentlig kemisk reaktion med den cirkulerende væske og den tilstedeværende CO 2. I stripperen hæves temperaturen af den cirkulerende væske, hvilket medfører, at optagne CO 2 atter frigives. For yderligere information om opgradering henvises til [2] og [3] Opgraderingspriser I forbindelse med ForskNG projektet Biogas til nettet [2], er udført en detaljeret beskrivelse af opgraderingspriser. Denne er udført med udgangspunkt i en biogasproduktion på 650 m3/h. I 2008 udgav Frauenhofer en rapport hvori opgraderingspriser for forskellige anlægstyper og størrelser [4]. Omkostningerne er opdelt på drifts- og kapitalomkostninger. Som det fremgår af Figur 4, der viser opgraderingsomkostninger for forskellige anlægstyper og størrelser, falder den specifikke opgraderingspris (målt som cent

42 10 pr. kwh opgraderet gas) med stigende anlægsstørrelse indtil anlæggene når en størrelse på er med kapacitet større end 1000 m 3 biogas pr. time. Herefter falder prisen kun beskedent for større anlæg. Figur 4. Specifik opgraderingspris for forskellige anlægsstørrelser. Efter [3]. I det følgende er det derfor valgt at tage udgangspunkt data fra Fraunhofer. Forudsætninger gjort af Fraunhofer: Rente 6 % Afskrivningsperiode 15 år Antal driftstimer 8000 timer pr. år Metanindhold i biogas 53 % Elpris (15 cent/kwh) 1,12 kr/kwh I forbindelse beregning af omkostninger til opgradering af biogassen til naturgaskvalitet er der taget udgangspunkt i Fraunhofers data. Dog er der følgende ændringer. Der regnes med en elpris på 0,80 kr/kwh Det antages, at prisen på opgradering er den samme for en biogas med et metanindhold på 53 % og en biogas med et metanindhold på 65 % som er typisk for gyllebaseret biogas. For PSA anlæg og vandskrubberanlæg er denne antagelse rimelig. Det skyldes, at den væsentligste driftsomkostning for disse to teknologier er omkostning til elforbrug i forbindelse med komprimering af biogassen. Det betyder, at omkostninger pr. mængde opgraderet metan er højere for en biogas med et lavt metanindhold end en biogas med et højt metanindhold. For

43 11 et amin-anlæg udgør omkostningen til regenerering af skrubbermediet en væsentlig omkostning. Der betyder, at med de til rådighed værende oplysninger er det ikke umiddelbart muligt at vurdere hvor god denne antagelse er for aminvask.teknologien. Med denne teknologi er det dyrere at opgradere en gas med et høj CO2 indhold da der er mere CO2, der skal fortrænges fra skrubbermediet. Dvs. det er samme tendens som for de to øvrige teknologier. Det er valgt at tage udgangspunkt i en anlægsstørrelse på 1000 m3/h. For større anlæg f.eks m3/h er den specifikke pris stort kun lidt lavere end for et 1000 m3/h anlæg, jf. Figur 4. De forskellige leverandører af opgraderingsanlæg har anlæg i forskellige størrelser i deres produktportefølje. Et eksempel på dette er vist i Figur 5. Dvs. har man f.eks. et opgraderingsbehov på m3 biogas pr. time kan det stykkes af flere anlæg f.eks. 1 GR24, 2 GR12 og 1 GR6. Herved fås et system med en opgraderingskapacitet fra m3 biogas pr. time. Det store driftsområde vil i dette tilfælde være hensigtsmæssigt da opgraderingsanlægget ikke skal behandle en konstant mængde biogas, men en mængde der varierer afhængig af årstiden. Figur 5. Forskellige størrelser af opgraderingsanlæg fra Malmberg produktportefølje. På baggrund af ovenstående er størrelsen af de specifikke driftsomkostninger og de årlige kapitalomkostninger blevet bestemt for et 1000 m3/h anlæg, se Tabel 2. Af tabellen fremgår det at kapitalomkostninger i forbindelse med nettilsætningen udgør mere end 60 % af kapitalomkostningerne til selve

44 opgraderingen. Det skyldes at til måling og kontrol af gaskvalitet indgår og komprimering til 40 bar er medtaget under denne post. 12 Tabel 2. kapital og driftsomkostning for opgraderingsanlæg til behandling af 1000 m 3 biogas pr. time. Bestemt på baggrund af [3]. CarboTech (PSA anlæg) Malmberg MT Energie (vandskrub (Amin ber) anlæg) Kapitalomkostninger, opgradering. mio. kr/år 1,42 1,31 1,20 Kapitalomkostninger, Nettilsætning. mio. kr/år 0,84 0,84 0,84 Driftsomkostning opgradering kr/m3 CH 4 0,38 0,37 0,51 Driftsomkostning Nettilsætning kr/m3 CH 4 0,067 0,067 0,067 Dvs. at hvis der vælges et vandskrubberanlæg er der faste omkostninger på 2,15 mio. pr. år for et for et opgraderingsanlæg og nettilsætning med en kapacitet på 1000 m 3 biogas pr. time. Derudover er der driftsomkostninger svarende til ca. 0,44 kr./m 3 opgraderet metan. Den mængde biogas, der skal opgraderes og afsættes via naturgasnettet er forskellen mellem biogasproduktion og biogasforbruget på kraftvarmeværkerne. Med en biogasproduktion som forventet af Ringkøbing-Skjern Kommune på 60 mio. m 3 metan pr. år og det der forventes af kunne afsættes til kraftvarmeværker (se Figur 3), bliver den del af biogasproduktionen, der skal opgraderes som vist i Figur 6. Heraf ses der i perioden december til marts er biogas produktionen ikke tilstrækkelig til at dække varmebehovet, mens der i perioden april til november er en overproduktion at biogas i forhold til forbruget. I vinterperioden hvor den overskydende biogasmængde er negativ skal der suppleres med er andet brændsel.

45 Overskydende biogasmængde / m 3 NG ækv jan mar maj jul sep nov Figur 6. Overskydende biogasproduktion når kraftvarmeværkerne i området har dækket varmebehovet. Som det fremgår af Figur 6 er der i juli et overskud af biogas på omkring 2,3 mio. m 3 naturgas ækvivalenter forhold det forventede gasforbrug gasmotoranlæggene. Det svarer til ca m 3 biogas pr. time. Det betyder, at hvis hele denne biogasmængde skal opgraderes og distribueres via naturgasnettet vil opgraderingsanlægget kunne få ækvivalente fuldlaststimer pr. år. Det vil resultere i en opgraderingspris på 1,49 kr. pr. m3 metan. Det samlede biogas overskud er 10,9 mio. m 3 metan pr. år. Se Tabel 3. Heraf fremgår også at det koster 18 øre/m 3 produceret biogas at opgradere den del af produktionen, der ikke kan afsættes til kraftvarme. Tabel 3. Dimensionerende biogasmængde, antal fuldlaststimer og opgradereringspriser ved opgradering af biogassen, der ikke kan afsættes til kraftvarmeværker. Forventet afsætning Dimensionerende gasmængde Dimensionerende gasmængde m 3 /måned naturgas ækv m 3 /h biogas Ækv. fuldlasttimer h Opgraderingspris kr/m 3 CH 4 1,49 Opgraderingsomkostninger Mio. Kr./år 17,7 Kr./m3 biogas prod. Opgraderingsomkostninger 0,18

46 14 I stedet for at opgradere hele den overskydende biogasmængde, kan man vælge anvende en del af gassen i gasmotorerne, selvom der ikke er et varmebehov, der skal dækkes. Det betyder, at biogassen vil blive brugt elproduktion, mens varmeproduktionen må bortkøles. Herved vil man kunne nøjes med et mindre opgraderingsanlæg, der så vil få flere driftstimer og dermed lavere opgraderingsomkostninger. Af Tabel 4 fremgår det hvor meget opgraderingsomkostningerne falder ved reduceret opgraderingskapacitet og hvor stor en del af den overskydende biogas, der ikke opgraderes, men må anvendes elproduktion uden samhørende varmeproduktion. Tabel 4. Opgradereringspriser mv. ved forskellige opgradereringskapaciteter. Biogasaftag til gasmotorer er sat til det forventede jf. Figur 3. Opgraderingskapacitet m 3 /h (biogas) Ækv. fuldlasttimer h Opgraderingspris Kr./m 3 CH 4 1,49 1,39 1,30 1,23 Andel af overskud, der ikke opgraderes - 0% 10% 23% 41% Opgraderingsomkostninter Mio. Kr./år 16,3 13,7 10,9 7, Sæsonvarieret biogasproduktion Det er til vis grad muligt at sæsonvariere gasproduktionen fra biogasanlæg så den tilpasses varmebehovet på kraftvarmeværker. Det kan gøres ved at anvende en højere andel af biomasse med et forholdsvist højt gaspotentiale om vinteren og end om sommeren. Der er dog forskellige opfattelser af hvor meget det er mulig at sæsonvariere produktionen [5]. For at vurdere indflydelsen af en varieret gasproduktion er der udført beregninger med tre forskellige tænkte gasproduktionsprofiler. Fælles for dem er, at årsproduktionen er den samme som i de ovenfor beskrevne beregninger. Biogasproduktionen er tænkt sæsonvarieret sådan at produktion er hhv. 5, 10 og 15 % højere om vinteren i forhold til konstant produktion og 5, 10 og 15 % lavere om sommeren i forhold til konstant produktion De tre produktionsprofiler er vist i Figur 7 sammen med et profil svarende til konstant produktion og forventet biogasforbrug.

47 Biogasmængder / m 3 NG ækv jan feb mar apr maj jun jul aug sep okt nov dec Konstant produktion Forventet biogasforbrug +/- 5 % +/- 10 % +/- 15% Figur 7. Forventet biogasforbrug og forskellige tænkte produktionsprofiler. For alle produktionsprofiler er der regnet med at hele den overskydende biogasproduktion opgraderes. Resultatet er vist i Tabel 5. Heraf fremgår det at driftstimetallet vil øges markant hvis der er muligt sæsonvariere biogasproduktionen og som følge deraf vil de specifikke opgraderingsomkostningerne (kr. pr. mængde gas) falde fra 1,49 kr./m 3 opgraderet CH 4 ved konstant biogasproduktion til 1.20 kr./m3 CH 4 ved en sæson variation hvor produktionen reduceres om sommeren og øges om vinteren på 15 %.

48 Tabel 5. Effekt af sæsonvarieret biogasproduktion på opgraderingspris og anvendelse af biogassen. 16 Produktionsprofil ± 0% ± 5 % ± 10 % ± 15% Timer Opgraderings-kapacitet m3/h Opgraderingspris, Fuldlasttimer, opgraderingsanlæg. Opgraderingsomkostninger Opgraderingsomkostninger Anvendelse af biogassen kr/m3 CH4 Mio. Kr./år Kr./m3 biogas prod. 1,49 1,45 1,34 1,20 16,3 14,8 13,4 12,0 0,18 0,16 0,15 0,13 Kraftvarme 79,5% 80,8% 81,1% 81,2% Opgraderet 20,5% 19,2% 18,9% 18,8% Betydning af biogasmængde Som tidligere nævnt regner Ringkøbing Skjern Kommune med biogasproduktion svarende til 60 mio. m 3 metan pr. år. For at vurdere hvor meget opgraderingsprisen afhænger af den biogasmængde, der skal opgraderes, er udført beregninger med en reduceret gasproduktion. Det vil betyde, at der skal anvendes mere naturgas i vinterperioden og at der er en mindre biogasmængde, der skal opgraderes og afsættes via naturgasnettet. Hvis der i stedet for en biogasproduktion på 60 mio. m 3 metan regnes med 80 % af denne vil biogasmængden, der skal opgraderes falde markant. Af Figur 8 ses, at med den lavere biogasproduktion vil der kun være overskydende gas, der ikke kan afsættes til kraftvarmeværker i fire måneder om året. Det kræver naturligvis lavere opgraderingskapacitet, men også i færre ækvivalente fuldlaststimer og dermed højere specifik opgraderingspris - se Tabel 6.

49 17 Overskydende biogasmængde / m 3 NG ækv Forventet biogasproduktion jan mar maj jul sep nov Overskydende biogasmængde / m 3 NG ækv % af forventet biogasproduktion jan mar maj jul sep nov Figur 8. Overskydende biogasproduktion når kraftvarmeværkerne i området har dækket varmebehovet ved to forskellige biogasproduktioner. Tabel 6. Indflydelsen af biogasproduktion på opgraderingspris. Forventet produktion 80 % af forventet Dimensionerende m 3 /h gasmængde biogas Ækv. fuldlasttimer h Opgraderingspris Opgraderingsomkostninger Opgraderingsomkostninger Kr./m 3 CH 4 Mio. Kr./år Kr./m3 biogas prod. 1,49 1,79 16,3 9,4 0,18 0,13 6 Følsomhed overfor anden vedvarende energi. Anden VE end biogas, som solvarme, geotermi og biomasse, kan anvendes til at dække et varmebehov. Udnyttelse af anden VE vil have indflydelse på indpasningen af biogassen. Dette beskrives kort i det følgende Solvarme Der er stor interesse for anvendelse af solfangeranlæg til produktion af var-

50 18 me på kraftvarmeværker i Danmark. Da solindfaldet er størst om sommeren, hvor varmebehovet er mindst, vil solvarme kun kunne dække en begrænset del af varmebehovet med mindre der etableres sæsonlagre. Et dimensioneringsgrundlag, der har været anvendt flere steder er, at solvarmeanlægget skal dimensioneres til netop at kunne dække varmebehovet når varmeproduktionen fra solvarmeanlægget er størst. På Figur 9 er vist et typisk varmeproduktionsprofil for et solfangeranlæg. Figur 9.Sæsonvariation i varmeproduktion fra typiske solfangeranlæg i Danmark. Fra [6]. Der er regnet på nogle scenarier med forskellige produktioner af solvarme. Fælles for alle beregninger er at produktionsprofilet angivet i Figur 9 er anvendt. På de lokale kraftvarmeværker anvendes gas til hhv. produktion af el og varme på motoranlæg og til varmeproduktion på kedelanlæg. Ved anvendelse af Energiproducenttællingen er det bestemt at i 2006 blevet 62 % af energien i den forbrugte gas på kraftvarme anlæggene i område konverteret til varme. Det er denne varmeproduktion, der potentielt kan dækkes af solvarme eller anden VE. Det svarer til den lilla kurve benævnt Samlet varmegrundlag på Figur 10. Figuren viser biogasproduktion og biogasforbrug på kraftvarmeværker forbundet til biogasnettet samt varmegrundet for biogas i det tilfælde hvor 50 % af varmebehovet dækkes vha. solfanger i den måned med lavest varmebehov.

51 19 Figur 10. Biogasproduktion og biogasforbrug på kraftvarmeværker forbundet til biogasnettet samt varmegrundet for biogas i det tilfælde hvor50 % af varmebehovet dækkes vha. solfanger i den måned med lavest varmebehov. Tabel 7. Indflydelse af på opgraderingsomkostninger. Solvarmeandel - sommer 0% 25% 50% 75% 100% Dimensionerende gasmængde m 3 /h biogas Opgraderet Mio. m 3 CH 4 /år 10,9 13,1 16,4 19,7 23,0 Omkostninger til opgradering mio. kr/år 16,3 19,9 24,0 28,1 32,3 Omkostninger til opgradering [kr/m 3 biogas produceret] 0,18 0,22 0,26 0,31 0, Geotermi I den danske undergrund er der vand, der har en temperatur, der er tilstrækkelig høj til at det kan være interessant at anvende det til fjernvarme produktion. Princippet er illustreret i Figur 11. Varmt vand pumpes fra undergrunden et sted og det afkølede vand pumpe ned et stykke derfra. Udnyttelsen af varmen kan ske enten med eller uden brug af varmepumper.

52 20 Figur 11. Princippet i geotermisk varme Der er i dag to anlæg i drift og der er ansøgninger om e række flere anlæg, se nedenfor. De to anlæg i drift er: Thisted Produktion siden boringer, 1,3 km, 44 C og Margretheholm Produktion siden boringer, 2,6 km, 73 C. Derudover er givet tilladelse til et anlæg i Sønderborg og der er ansøgt om en række andre anlæg, bl.a. et anlæg i Viborg. Det er dog ikke alle områder der egnede til geotermi. Som det fremgår af Figur 12, er der f.eks. ikke noget potentiale for ydnyttelse af geotermi i Ringkøbing-Skjern Kommune. For det planlagte anlæg i Viborg planlægger man at prioritere biogas over varme fra geotermianlægget. Dvs. hvis varmegrundlaget er for lavt til at kunne aftage varmeproduktion fra kraftvarmeproduktion på biogas og geotermi prioriteres geotermi lavere og man stopper geotermiproduktionen når

53 21 det er tilfældet. Tilsvarende stopper man i Thisted geotermianlægget når varmeproduktionen fra affaldsanlægget dækker varmebehovet,. Figur 12. Geotermipotentialer i Danmark. Fra [7].

54 22 Figur 13, Driftsfilosofi for det planlagte geotermianlæg i Viborg. Fra [8]. Figur 14, Fordeling af varmeproduktion for Thisted Varmeforsyning i Fra [9] Biomasse Biogasbaseret kraftvarme og varme- eller kraftvarmeproduktion baseret biomasse som flis eller halm. Som det er illustreret på Figur 14, behøver

55 23 ikke at konkurrere om det samme varmegrundlag. Disse brændsler er lagerstabile og kan derfor gemmes til der er behov for varmen. Hvis der er modstridende interesser der gør at der bliver produceret varme på biomasse som fortrænger varmegrundlag for biogasanlæg, vil det svare til et scenarie med lavere andet forhold mellem varmegrundlag og biogasproduktion. Se afsnit

56 24 7 Referencer [1] Nedgradering af gaskvaliteten i naturgasnettet. DGC Rapport, R0905, [2] Biogas til nettet. DGC Rapport, R0904, [3] Petterson, A. et al. Biogas upgrading technologies developments and innovations, IEA report October 2009 [4] Urban W, Girod K, Lohmann H. Technologien und Kosten der Biogasaufbereitung und Einspeisung in das Erdgasnetz. Ergebnisse der Markterhebung Fraunhofer UMSICHT [5] Øget produktion og anvendelse af biogas i Danmark Rammebetingelser og tekniske forudsætninger. DGC Rapport, R0906, [6] Technology data for energy plants. June Energinet.dk and Danish Energy Agency. %20publikationer/2010/Technology_data_for_energy_plants.pdf [7] Geotermi i Danmark, konferenceindlæg af Søren Frederiksen, Energistyrelsen. IDA arrangenment [8] Geotermianlæg i Viborg indlæg af Henry Juul, Viborg Fjernvarme. IDA arrangement [9] Thisted varmeforsyning a.m.b.a. Årsrapport 2008, Driftsbudget 2009.

57 Appendix 2 Forøget biogasandel i energisystemet -Behov for systemydelser Written by DGC

58

59 DGC-notat 1/19 Forøget biogasandel i energisystemet Behov for systemydelser Torben Kvist Projektnotat December

60 DGC-notat 2/19 INDHOLDSFORTEGNELSE INDLEDNING... 3 ANVENDELSE AF BIOGAS... 3 BIOGAS OG GASSYSTEMET... 4 Forudsætninger... 4 Det danske gassystem... 5 Indflydelse af biogas på gassystemet... 6 Forbrugere... 6 Distributions- og fordelingsnet... 7 Transmissionsnettet... 8 Gaslagre... 8 BIOGAS OG ELPRODUKTION Samfundsøkonomisk værdi af prisfleksibel elproduktion...14 Værdi af lagring af biogas REFERENCER... 19

61 DGC-notat 3/19 Indledning I Danmark anvendes biogas primært til lokal kraftvarme. Andre steder som f.eks. i Sverige og Tyskland anvendes gassen også til andre formål. I disse lande raffineres en del af biogassen kaldet opgradering sådan at gassen opnår en kvalitet svarende til naturgas. Det muliggør, at biogassen kan anvendes i transportsektoren eller afsættes via naturgasnettet på lige fod med naturgas. Biogassen produceres i en nogenlunde jævn strøm henover året. Det er dog muligt til en vis grad at sæsonvariere biogasproduktionen. På de danske biogasanlæg er der ofte installeret et gaslager, der kan indeholde nogle timers gasproduktion og på de kraftvarmeværker, som anvender biogassen, er der typisk installeret varmelagre, der kan lagre op til et par dages varmeproduktion. Det giver en vis, men begrænset, fleksibilitet i forhold til at kunne producere el og varme i forhold til aktuelle behov. Hvis biogassen opgraderes og afsættes via naturgassystemet, vil dette system kunne fungere som lager for biogassen. I modsætning til el, der ikke lagres, og varmeproduktion, der lagres op til et par dage, tilbyder naturgassystemet mulighed for længere tids lagring af biogas. Denne mulighed har dog en pris, idet det kræver, at biogassen opgraderes til naturgaskvalitet ligesom der er omkostninger forbundet med selve lagringen. Formålet med dette notat er at vurdere, hvordan biogasproduktion passer ind i de eksisterende el- og gassystemer. Det vurderes, om biogasproduktion aflaster eller belaster de eksisterende systemer. Anvendelse af biogas Som nævnt anvendes biogas i Danmark primært til kraftvarmeformål, hvor hele elproduktionen afsættes til elsystemet, og den tilhørende varmeproduktion afsættes via fjernvarmesystemet. Det sker ved, at biogassen afbrændes i gasmotorer. Fordelen ved dette er, at man undgår at afsætte biogassen til naturgasnettet og dermed omkostningen, der er forbundet med at opgradere til naturgaskvalitet. Ulempen er, at man er begrænset af størrelsen af det lokale varmebehov. Der bortkøles i dag i gennemsnit en varmemængde svarende 15 % af den samlede biogasproduktion [1].

62 DGC-notat 4/19 Biogas og gassystemet Forudsætninger For at kunne vurdere betydningen af biogas for behovet af systemydelser er det nødvendigt at gøre nogle antagelser og opstille nogle forudsætninger. I forbindelse med dette arbejde opstilles følgende forudsætninger: Biogas, der anvendes på kraftvarmeværker, kan sidestilles med naturgas. Det indebærer, at det er antaget, at el- og varmevirkningsgrader er som for anvendelse af naturgas. Det betyder, at biogas kan erstatte naturgas i forholdet 1:1 (på energibasis). Gassystemet vil i nær fremtid se ud som nu. I dag er naturgasforbruget total dominerende i forhold til biogasforbruget. Der bruges 165 PJ naturgas og ca. 4 PJ biogas pr. år [2]. Naturgasforbruget er svagt faldende, og det forventes, at biogasproduktionen vil stige i fremtiden. Det er forudsat, at naturgassen også fremover vil være dominerende i forhold til biogas. Det betyder, at selvom der tilsættes biogas til naturgassystem, vil det ikke ske i mængder, der grundlæggende vil ændre systemet. Lokalt kan der dog blive tale om forholdsvis store mængder biogas, så naturgassen visse steder ikke længere vil være dominerende. Der vil stadig være naturgasproduktion i Nordsøen, og man vil stadig have behov for en forbindelse til Tyskland og Sverige. Gasforbruget er upåvirket af, at biogas opgraderes og injiceres i naturgassystemet. Det betyder, at den biogas, der måtte blive injiceret i naturgasnettet, vil fortrænge en tilsvarende mængde naturgas (på energibasis).

63 DGC-notat 5/19 Figur 1. Energistyrelsens og Energinet.dk s fremskrivninger af naturgasforbruget i Danmark. Fra [5]. Det danske gassystem Nedenstående beskrivelse er baseret på [4]. Det danske gastransmissionssystem består af opstrømsrørledninger i den danske del af Nordsøen, og af transmissionsledninger på land. Transmissionsledningerne går på langs (Aalborg-Ellund) og tværs Nybro-Dragør) af Danmark, og distributionsledningerne består af et net af rørsystemer ud til forbrugerne. Herudover består gastransportsystemet af et gasbehandlingsanlæg (Nybro) og to underjordiske gaslagre (Stenlille og Lille Torup), se Figur 2. Figur 2. Overordnet gasinfrastruktur i Danmark. Fra [4]. Naturgassen fra den danske del af Nordsøen transporteres i land nord for Esbjerg ved et tryk på op til 138 bar. På land passerer naturgassen gennem et gasbehandlingsanlæg i Nybro. Her kontrolleres og måles gaskvaliteten, og trykket reduceres til det maksimale landledningstryk på 80 bar.