Cogeneration opportunities for increasing energy efficiency. Villu Vares

Transcription

1 Cogeneration opportunities for increasing energy efficiency Villu Vares

2 Topics! Cogeneration in Europe! Technologies, power to heat ratio, efficiency! DH heat sources base and peak load! Example of biofuel based CHP feasibility estimation! New cogeneration technologies based on biomass gasification

3 Share cogeneration in power generation CHP in Estonia: about 10% of electricity and 30% of heat

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5 Power plants in European Union

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7 Sankey diagrams for condensing and CHP thermal power plants

8 Carnot thermodynamic cycle efficiency of " c =1# T 2 T 1 = T 1 # T 2 T 1! T 1 =t max temperature! T 2 =t min temperature

9 Carnot thermodynamic cycle efficiency examples T1 t1 T2 t2 eetac % % % % % % %

10 Steam cycle CHP, heat load district heating

11 Cogeneration using gas turbine

12 Combined cycle cogeneration gas turbines and steam turbine

13 Cogeration using reciprocating engine

14 Efficiencies of power technologies 85% 86% 86% 88% 41%

15 Operational parameters of cogeneration technologies Unit capacity P, MW! el, % on loads 100% 50%! total, % P/Q Steam cycle 0, ,1-0,5 Gas turbine 0, ,5-0,8 Diesel engine 0, ,8-1,0 Otto Otto engine 0, ,5-0,7 Fuel cell 0, ,8-1,0 Stirling engine 0,003-1, ,2-1,7

16 Diesel engines power to heat ratio

17 Steam cycle CHP power to heat ratio dependence of steam parameters Power to heat ratio 0,7 0,6 0,5 0,4 0,3 0,2 Pressure of fresh steam 40 bars Pressure of fresh steam 100 bars Pressure of fresh steam 180 bars 0,1 0 0,4 0,8 1, Back-pressure in bars

18 Operational control in cogeneration plants! Control might be arranged in correspondance with heat load or with power load : " In Scandianvia and in Eastern European contries operational control is arranged in correspondance with heat load i.e. power output depends on heat load " operational control might be arranged also in correspondance with electricity load i.e. heat output depends on electricity demand. If heat cant be used steam should be condensed like in condensing plants! Recommendation: CHP plants should be planned according heat load

19 Heat duration curve for district heating

20 Heat sources for district heating Base load! Cogeneration plants! Biomass or other solid fuel boilers! Waste inceneration plants! Waste heat from industry Characteristics! High level of investmets! Low fuel price! Not flexible in operation! Slow start Peak load! Gas boilers! Oil boilers! Electric boilers or heaters Characteristics! Lower investments! High fuel price! Flexible in operation! Quick start

21 Recommendations for CHP planning Source: A.Nuorkivi, CHP Handbook, 2002! Optimal thermal capacity of solid fuel CHP in DH network is 10 20% of max heat load. High investments into CHP plant are economically feasible if utilisation time is long (plant is loaded as much as possible)! Optimal thermal capacity of gas turbine or gas engine CHP plant in DH network is 15 40% of max heat load,the bigger share migh be achived in case of gas turbines! If there are few types of CHP plants in DH network one of them should correspond with summer time heat load and other CHPs should work on gas or LFO, then CHP plants can cover up to 45 60% of max heat load

22 A.Nuorkivi illustration of recommendations

23 Electricity generation costs in case of different technologies wood fuel Source: The Future of CHP in European Market, 2001

24 Allocation of CHP costs to power and heat Heat Total Costs = Constant C D? B A Electricity

25 Allocation of CHP costs to power and heat A: Production of DH used to begin with extracting steam from the existing condensing power plants at low incremental costs and such costing was used quit a long time to compete with gas heating. (used to be in Denmark and Germany); B: District heating and power operate on a saturated market and the costs are allocated to power and heat in a market price based way (Finland and Sweden); C: Heat covers most of the costs of CHP and electricity is based on incremental costs (used to be in Poland, the Baltic countries and in Russia); and, D: Any method without regulation: when both the heat and power sectors are unbundled and competition works properly on both sides, no central regulation is needed but the market takes care of fair allocation of the CHP costs.

26 Contract between CHP and DHE*! Co-operation between the CHP company and the DHE should not be restricted to the level of operational heat trading contract only. Due to the various technical and economic connections between the systems, the total optimisation of CHP/DH system development and operation should be managed either by one organisational body, or in the other case, with a complete and comprehensive contract.! Example: In a CHP/DH system the heat load may decline either due to DH system rehabilitation and the consecutive energy savings or due to customers escaping to other heating systems. At the same time, the CHP plant should carefully consider, whether increasing of CHP capacity is optimal to meet the declining heat load. To avoid problems, both parties should work together to improve the CHP/DH system performance, thus keeping the existing and attracting new customers. * DHE District Heating Enterprise

27 EU COGENERATION DIRECTIVE DIRECTIVE 2004/8/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 11 February 2004 on the promotion of cogeneration based on a useful heat demand in the internal energy market and amending Directive 92/42/EEC Member States may implement different support mechanisms for high-efficiency cogeneration at the national level, including investment aid, tax exemptions or reductions, green certificates and direct price support schemes

28 Determination of cogeneration efficiency! High-efficiency cogeneration shall fulfill the following criteria: " cogeneration production from cogeneration units shall provide primary energy savings of at least 10 % compared with the references for separate production of heat and electricity, " production from small scale and micro cogeneration units providing primary energy savings may qualify as high-efficiency cogeneration.

29 ! micro-cogeneration unit shall mean a cogeneration unit with a maximum capacity below 50 kwe! small scale cogeneration shall mean cogeneration units with an installed capacity below 1 MWe

30 Cogeneration technologies covered by this Directive (a) Combined cycle gas turbine with heat recovery (b) Steam backpressure turbine (c) Steam condensing extraction turbine (d) Gas turbine with heat recovery (e) Internal combustion engine (f) Microturbines (g) Stirling engines (h) Fuel cells (i) Steam engines (j) Organic Rankine cycles (k) Any other type of technology or combination them

31 Electricity production from cogeneration shall be considered equal to total annual electricity production of the unit measured at the outlet of the main generators! in cogeneration units of type (b), (d), (e), (f), (g) and (h) referred to in previous slide, with an annual overall efficiency set by Member States at a level of at least 75%, and! in cogeneration units of type (a) and (c) referred to in previous slide with an annual overall efficiency set by Member States at a level of at least 80 %.

32 Calculation of electricity from cogeneration E CHP = H CHP!C E CHP amount of electricity from cogeneration C power to heat ratio H CHP amount of useful heat from cogeneration (calculated for this purpose as total heat production minus any heat produced in separate boilers or by live steam extraction from the steam generator before the turbine)

33 The calculation of electricity from cogeneration must be based on the actual power to heat ratio. If the actual power to heat ratio of a cogeneration unit is not known, the following default values may be used: Type of the units Combined cycle gas turbine with heat recovery Default power to heat ratio 0.95 Steam backpressure turbine 0.45 Steam condensing extraction turbine 0.45 Gas turbine with heat recovery 0.55 Internal combustion engine 0.75

34 Calculation of primary energy savings (PES) " & $ 1 $ PES = # 1! CHPH! Re fh! + CHPE! ' $ $ % $ Re fe! ( $ )100% PES primary energy saving RefH! efficiency reference value for separate heat production RefE! efficiency reference value for separate electricity production

35 CHPH! heat efficiency of the cogeneration production defined as annual useful heat output divided by the fuel input used to produce the sum of useful heat output and electricity from cogeneration. CHPE! electrical efficiency of the cogeneration production defined as annual electricity from cogeneration divided by the fuel input used to produce the sum of useful heat output and electricity from cogeneration.

36 Heat demand scenarios for Estonia Heat for technological processes Heat for local heating Network losses Heat for district heating

37 Suitability of CHP technologies in case of different fuels! Natural gas all technologies might be used in wide capacity range. Gas turbine, gas engine or combined cycle high power to heat ratio and high efficiency could be reached! Biofuels and waste mainly steam cycle could be used, P/Q ratio depends on steam parameters (indirectly on as well on unit size!!!). According A.Nuorkivi this technology could cover 10 20% of max heating load and generate up to ca 30% of total heat demand

38 Example estimation of economical feasibility od wood based CHP units Large scale plant Small scale plant Electrical capacity, MW 17 3,5 Thermal capacity, MW Personnel 30 8 Investments, MEEK Payback time, years 5,3 8,6 NPV, MEEK IRR, % 18,0 9,8

39 Input data! Heat price 450 EEK/MWh;! Electricity price 1150 EEK/MWh (legally fixed!!!);! Price of wood chips 169 EEK/MWh = 127 EEK/m 3 loose ;[1]! Discount rate 5%;! Lifetime 20 years;! Total efficiency 86,5%;! Utilisation time 6000 h/a;! Personnel costs EEK/person;! Steam boiler based on fludised bed technology, back pressure turbine without without additional condensor, i.e 100% of heat output should be used for district heating! [1] Price in July EEK/m 3 loose (calorific value 0,75 MWh/ m 3 loose )

40 Elektri tootmishind, EEK/MWhe Sensibility Tundlikkuse analyse analüüs Plant Jaam 1: 1717MWe MWe/40 / 40MWth Increasing fuel prices Increasing investments Electricity generation costs Decreasing investments Decreasing fuel prices h/a

41 Electricity generation costs, EEK/MWhe Sensitivity analysis Plant 2, 3,5MWe / 16MWth Increasing fuel prices Increasing investments Electricity generation costs Decreasing investments Decreasing fuel prices h/a

42 New cogeneration technologies with gasification of biomass Villu Vares

43 Biomass conversion technologies See also next slide

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45 Benefits of gasification! after gasification of solid fuels gas might be transported through pipelines! clean technology - bad components could be removed in gasification process! high efficiency while combusting produced gas! produced gas might be used as a fuel in gas engines and gas turbines, i.e high power to heat ratio in comparison with steam cycle CHP! produced gas might be used as raw material in chemical industry (for production of vertilisers, etc) and as transport fuel

46 Gasification process

47 Gasification process depends on fuel properties! moisture content;! ash content and ash properties;! chemical composition;! calorific value;! bulk density and morfology;! volatile content;! content of N, S, Cl, alkali metals, hard metals etc

48 Steps from fuel receiving until gasification and electricity generation

49 Requirements depending gasification technology Gasification technology Downdraft Updraft Fluid bed Entrained flow Size (mm) < 1 Moisture (% in asreceived fuel) Ash content (% in dry fuel) < 60 < 40 < 15 < 5 < 15 < 20 < 20 Morphology uniform almost uniform uniform uniform Bulk density (kg/m 3 ) > 500 > 400 > 100 > 400 Ash melting point (ºC) > 1250 > 1000 > 1000 > 1250

50 Downdraft and updraft reactors

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52 Bubling (left) and circulating fluidized bed atmospheric pressure gasification reactors

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54 Operational characteristics Downdraft Updraft Bubling fluid bed Circulating fluid bed Entrained flow Temperature, ºC < 900 < 900 ca 1450 Tar content low high moderate moderate very low Control simple very simple moderate moderate Complicated C a p a c i t y, MW th Sensibility on fuel properties < 5 < ?? >100 less critical critical less critical less critical only fine fractions

55 Investments of biogas based combined cycle (gas +steam turbine) electricity generation plants

56 Typical investment costs of biogas firing plants

57 Typical electricity price from biogas based plants

58 Capital costs of new technologies and learning effect

59 Electricity generation costs! steam cycle! gt gas turbine;! ge gas engine;! I pressurised direct gasification with hot gas cleaning;! II atmospheric direct gasification with gas cooling and wet cleaning;! III atmospheric indirectly heated gasification and gas cleaning in scrubbers

60 Used data in the analyse! amortisation period 13 aastat;! discount rate 6%! inflation 2%;! reactor of the year 2008;! fuel price 14 EUR/MWh;! utilisation time 7600 h/a

61 Some conclusions! Gasification allows utilisation of problematic fuels for enegy generation! Expensive technologies, commercial plants are not available, some pilot plants are in operation