Layman Report. Stirling Power Station. Mini CHP with longlife Stirling engine. Mayer & Cie. GmbH & Co. P.O. Box D Albstadt

Transcription

1 Stirling Power Station Mini CHP with longlife Stirling engine Project LIFE99 ENV/D/ GmbH & Co. P.O. Box D Albstadt

2 1. Contents 2. Key words 3. Summary 1. Contents 2 2. Key words 2 3. Summary 2 CHP versus oil/gas boilers and oil/gas calorific value boilers 3 4. Motivation 6 5. Technical development 8 6. Progress & results 9 7. Future prospects 10 Small-scaled CHP unit; cogeneration; Stirling engine; CO 2 reduction; residential cogeneration; domestic energy; heating system; gas burner; longlife; high availability; 1 3 kw current; Project aim Tests & measurements The aim of the project is to develop a mini combined heat and power plant (mini-chp) on the basis of a Stirling engine. With a rating of 1 to 3 kw electrical power and up to 15 kw thermal output, this mini CHP is suitable for supplying detached and semi-detached houses and apartment buildings, as well as small commercial operations. To date, the machines have been operated in tests and measurements for a total of approximately 40,000 hours, achieving and verifying the desired electrical power of up to 3 kw el, with an efficiency of over 18 % in relation to the complete system. The efficiency of the complete system, at 85 %, was achieved and confirmed repeatedly. Fig.1: Mini CHP system Fig.2: Stirling engine MCT LIFE99 ENV/D/

3 CHP versus oil/gas boilers and oil/gas calorific value boilers Various attempts have been made to compare the efficiencies of oil/gas boilers and oil/gas calorific value boilers, which effectively offer efficiencies of over 100 %, and sometimes up to 109 %, with a CHP. A comparison of this type is inadmissible and also wrong, for five reasons. First: In contrast to a CHP, oil/gas boilers and oil/gas calorific value boilers are not able to produce heat and electricity simultaneously. Second: An exclusively German peculiarity is the specification of the efficiencies for calorific value boilers and low temperature heating boilers. This serves simply to enable a competitive comparison between the individual boilers and heaters. This involves adding the energy gain from the exhaust gas condensation to the actual technical efficiency (the equipment efficiency) of the heating boiler, which must always be below 100 %, otherwise it would be a perpetual motion engine. With this relatively new technique, the condensation of the water vapour contained in the exhaust gas is not prevented, but deliberately encouraged. Not only the actual (tangible), but also the latent energy (stored in the water vapour) of the fuel is used for hot water heating inside the boiler. The exhaust gases are cooled by means of specially shaped heat exchangers until the water vapour contained in them condenses and releases useful heat. The heat proportion is dependent on the fuel. In the case of heating oil, it makes up approx. 6% of the heat energy contained in the exhaust gas, and up to 11 % in the case of natural gas. Without the use of calorific value technology, this heat energy would simply be lost via the chimney. The technical efficiency - the equipment efficiency - of oil/gas boilers and oil/gas calorific value boilers, is between 85 and 98%, depending on the type, the technology used, the insulation and year of manufacture. Only by adding the energy gained from the exhaust gas through condensation to the energy generated in the boiler can "efficiencies" with values of over 100 % be achieved as product-specific comparison values. Example "without" calorific value technology Example "with" calorific value technology LIFE99 ENV/D/

4 Third: Fig. 3: Comparison of primary energy utilisation and losses for central and decentral energy generation CHP and its ecological and monetary advantages Private households are one of the world's largest energy consumers. The practice of the separate generation of electrical energy in electric supply stations and heat in the home, which is still the norm today, is a waste of primary energy, and contributes considerably to global warming; on top of this, is the environmental pollution due to emissions. An accommodation unit in an average detached house requires an annual average of approx. 4,400 kwh electricity, plus around 21,500 kwh for heating and water heating. In order to provide the 4,400 kwh demanded at the socket, a power station with an efficiency of 38 % and the addition of 2% transmission losses, must expend approx. 12,220 kwh primary energy. This corresponds to 1,222 litres heating oil. The electric supply station simultaneously releases approx. 2,400 kg CO 2. For a domestic heat requirement of 21,500 kwh, a new oil or gas boiler with a technical efficiency of 90 % expends approx. 23,890 kwh primary energy. This corresponds to approx 2,389 litres heating oil or 2,684 m³ natural gas. Depending on the combustion quality, between 2,600 and 4,000 kg CO 2 are released simultaneously. Adding these figures together, at present 36,110 kwh primary energy is needed to supply an average detached house, of which just 25,900 kwh is effectively used. 10,210 kwh corresponds to 1,021 litres heating oil or 1,147 m³ natural gas. Over 31 % are losses in this example, which are either discharged as hot water into the rivers, or as heat in exhaust gases into the environment. In the case of decentralised electricity and heat generation with a micro CHP, effectively used where the energy is required, the primary energy consumption and harmful emissions are considerably reduced. Instead of 36,110 kwh primary energy (power station plus domestic consumption), on the basis of the above application examples (heat requirement kwh) and taking account of an efficiency of 85 % for the CHP, only 25,294 kwh primary energy is required. The resulting primary energy saving is thus 30 %. 5,059 kwh electricity is generated as a secondary product during the heat production, and remunerated by means of special legislation (see economic efficiency calculation in Appendix). LIFE99 ENV/D/

5 Fourth: Fifth: Today, with conventional technology, the environment is additionally polluted by approx. 2.4 tons CO 2 from the generation of power in electric supply stations, plus 2.6 to 4.0 tons CO 2 (depending on the combustion quality) from domestic heat generation, in total: 5 to 6.4 tons, per accommodation unit and p.a.. With a micro CHP, with simultaneous generation of electricity and heat, only approx. 3.4 tons CO 2 are generated per unit and p.a.. The potential reduction in CO 2 emissions is thus approx. 32 to almost 50% with use of a micro CHP. Highly significant for reducing emissions is the development of a special gas blower burner (ERTeC burner), implemented for the operation of mini-chps, which is equipped with calorific value technology like conventional calorific value boilers, and on its own has an "equipment efficiency" of currently 107 %. The combustion technology developed within the ERTeC burner, which takes place at constantly high temperatures (approx. 800 C) with a high efficiency (98 %) and simultaneously high exhaust gas recirculation (speed approx. 350 km/h), considerably reduces the development of emissions. Such low emission values cannot be achieved with any other combustion system, even with the aid of catalysts or lambda sensors. Comparison of exhaust gas emissions [mg/m³] CO NOx Clean Air Guidelines CHP with catalytic converter CHP with catalytic converter and lambda probe DIN 4702 fuel value units Blue Angel U41 units Stirling with ERTeC burner Conclusion Fig. 4: CO and NO x emissions in exhaust gas after combustion in different systems Through the simultaneous, coupled production of electricity and heat, in small, local systems (= CHP), primary energy can be saved and CO 2 emissions significantly reduced! This cannot be achieved with any other conventional heating system. LIFE99 ENV/D/

6 4. Motivation Germany's households alone release 125 million tons *) CO 2 into the atmosphere via chimneys year after year Inevitable consequence: Greenhouse effect. *) Source: Stat. Yearbook for the FRG Through simultaneous (coupled) production of electricity and heat in small, local systems primary energy can be saved and emissions significantly reduced; this protects the environment and saves you money. CO 2 saving The saving in primary energy which can be locally achieved with a Stirling CHP is %, plus corresponding quantities of CO 2. Depending on the type of power plant on which a calculation is based, for each small office building or detached house that is equipped with a Stirling CHP, 2,650 to 4,000 Kg CO 2 can be saved p.a.. Fig. 5: System comparison: central and local energy supply Cogeneration is the process that takes place within the mini CHP: Cogeneration The flame of a specially developed gas burner heats the heater head of the Stirling engine from outside. The latter drives an integrated generator in the crank casing to generate electricity. The cooling water of the engine is used for heating and service water heating. The turnkey system consists of a low CO 2 and NO x ERTeC burner, a Stirling/generator unit, a buffer memory and a control and feedback control unit. LIFE99 ENV/D/

7 Requirements By defining the development objective, the fundamental requirements can also be described. The aim is to develop a system which offers a substitute to conventional heating in a detached house (DH) and provides additional heating in larger buildings (semi-detached house, small businesses, hotels, etc.), whilst simultaneously generating electricity. It must ensure a fully automatic, reliable, safe, low-maintenance operation during its overall operating life. In the case of a heating system for a DH, the latter is 15 years. For a CHP system, this means: The lifetime must be 30,000 hours or more. For comparison: If a car could be driven for an average of 30,000 hours at 50 km/h, this would correspond to 1,500,000 km. In addition, within the 30,000 car operating hours or the mileage of 1,500,000 km, the car would have to be serviced 60 to 75 times (depending on the manufacturer) and the required maintenance costs paid for. In contrast to the average lifetime of a car, which is around 200,000 km, the lifetime of a CHP is around 8 times greater than that of a car - without the need for maintenance. Profitable The investment costs necessary for such a unit may only be so high, that everyone can afford such a system. For use in a DH the CHP system has to be profitable. I.e.: The amortisation period must be shorter than the expected operating life. In applications which have annual operating periods of 6,000 hours and more, operational amortisation calculations have shown that amortisation periods between 2 and 4 years are achieved. Furthermore, there are additional demands that can be made on a CHP heating system in a DH. In this respect, one could mention noise and odour generation, easy operation and complexity. The complete system must be supplied ready for installation, the construction must be easy to realise and there must be no mandatory special installations or special authorisations for operation. It goes without saying that the unit meets valid standard and approvals. Enormous market potential Such a CHP system may only be used to supply a DH once all these requirements are met. By using CHP in a DH, an adequate market potential can be achieved, which enables the series production of Stirling engine CHP systems in the appropriate quantity, as well as enabling economic production and, consequently, an attractive purchase price for the end customer. LIFE99 ENV/D/

8 5. Technical development In order to meet these requirements, the following technical conditions have been determined: Stirling engine, β-type helium-sealed, dry-run, safe to operate, lowmaintenance operation with over 30,000 hours Asynchronous generator for power generation directly coupled to the grid and which serves as starter switch at the same time. Low NOx ERTeC*- natural gas burner with air-preheating, which does not require a peak load boiler in a detached house. * "Exhaust Recirculation Temperature Converter" MCFCC, Measurement, Control, Feedback Control and Communication unit, which enables and monitors fully-automatic operation; Performs safety shut-downs; Records and transfers measurement data, as well as enabling external communication. Market entry can only occur when all requirements are fulfilled. The development work was divided into two fundamental phases in the project. During the first phase, the key activities concentrated on the actual Stirling engine. Four prototypes were built and tested, based on experiences with a functional model. The aim was to develop a basic Stirling engine module and to prove the fulfilment of all requirements defined for the application in test operation. During the second phase, activities focused on the development and implementation of the overall CHP system, i.e. the development and manufacture of a module with all functions required of a turnkey, fully-automatic, functioning CHP module Fig. 6: Stirling engine MCT on test bench and measurement print screen LIFE99 ENV/D/

9 6. Progress & results The aim of the project was achieved. The efficiency and performance statements were provided. Achievement of the target capacity of up to 3 kw el with an overall effectiveness of over 18% was verified in test mode, with achievement of an efficiency of over 85% (without taking account of the calorific value utilisation). The aim of the project was achieved New burner technology ERTeC Fig. 7: Performance statement Stirling Mini CHP A basic module of the CHP system is now available, which enables fully automatic operation and fulfils the requirements of the relevant regulations. In detached houses and small consumers, this is connected to the normal natural gas pipeline with 22 mbar pipe admission pressure. All necessary components such as burner, gas feed line and control components are matched to this line pressure. Connection to the existing heating system via a hot water buffer tank is expedient. This optimises operation times. Connection to the public grid occurs directly via a so-called feed-in meter. The installation cost is no higher than for conventional gas heating. The extremely low exhaust gas values of the Stirling Mini CHP are striking. This is achieved by using a new burner technology, "ERTeC burner ". To increase overall effectiveness, a gas burner with integrated fresh-air-preheating was developed. The hot exhaust gases pre-heat the cold aspirated fresh air. Simultaneously, the exhaust gas is cooled to approx. 60 C. Thus the burner works according to the fuel value principle. The resulting condensate can be fed into the drainage system without any problem in accordance with the existing legislation. Through preheating, the necessary gas use can be reduced, primary energy can be saved and a high effectiveness can be achieved. Due to the high degree of internal exhaust gas recirculation, the extent of applicable exhaust gas provisions is significantly reduced. Thus only NO x values of under 25 ppm can be achieved with this principle. With a current commercially approved gas blower burner, neither the exhaust gas values, nor the necessary high efficiency can be achieved. The ERTeC burner thus makes possible what was impossible for previous burners: High efficiencies at temperatures of over 800 C. LIFE99 ENV/D/

10 The heart of the system is the Stirling engine type MCT Even during the conception phase, the conditions required for use as a reliable, longlife, lowmaintenance and high-performance drive unit, which is also affordable, in a Reliable, longlife, low-maintenance and highperformance Stir-minling engine value was placed on a production and installation oriented design, which was CHP for supplying a detached house, were taken into account. Special suitable for series production. This was the only way to achieve the cost objective for the complete system. 7. Future prospects All models, tools and fixtures required for manufacture are designed for series production. The complete documentation required for series production is Ready for also available; e.g. purchasing requirements, production and quality assurance series production regulations. In addition, the costing provided the proof that with a production batch size of 1,000 units p.a., the target sales price should be achievable for an end customer. Cost comparison: Gas calorific value Stirling mikro-chp Annual costs Costs 3, Costs Purchase of electricity Annual cost saving over Annual costs 2, , , , , , Fuel costs Annual saving , , Gas calorific value Stirling micro-chp Annual saving: Investment costs Sale of electricity electricity costs avoided Eco tax reimbursement Fig. 8: Cost comparison (extract from an extensive energy requirement and economic efficiency calculation "Mini CHP Plan" for a semi-detached house) LIFE99 ENV/D/

11 1. ECONOMIC EFFICIENCY CALCULATION Conventional calorific value boiler or micro CHP using a semi-detached house as an example Original data.1 Net heat requirement kwh 42, Net electricity requirement kwh 8, Energy supply costs, natural gas /kwh Energy supply costs, electricity /kwh Mineral oil tax, natural gas /kwh Ecological tax, electricity /kwh Remuneration - electricity feed-in /kwh Remuneration - grid utilisation /kwh Remuneration - CHP Act bonus /kwh Gas condensing boiler Micro CHP 2. Capital expenditure 15 kw therm 3 kwel / 15 kw therm.1 Capital expenditure 5, , Efficiency System costs.1 Amortisation period Years Cost-accounting depreciation 333, (Line 2.1 / Line 3.1).3 Energy requirement, gas kwh ,412 [Line 1.1 / Line 2.2).4 Energy supply costs, gas 1.569,47 1, (Line G 1.3 x Line 3.3).5 Energy supply costs, electricity 1.148,40 1, [Line 1.2 x Line 1.4).6 Annual running time Hours ,294 (Line 3.3 / therm. output 15 kw).7 Electricity production kwh ,882 (Line 3.6 x electr. output 3kW).8 Mineral oil tax refund (Line Mi 1.5 x lö Line 3.3) t.9 Electricity ecological tax refund (Line 1.6 x Line 1.2).10 Reimbursement, electricity feed-in (Line 1.7 x Line 3.7).11 Reimbursement, reduced grid use (Line 1.8 x Line 3.7).12 Reimbursement, CHP Act bonus (Line 1.9 x Line 3.7).13 Total system costs 3, , t 4. Profitability calculation.1 Profit.2 Profitability %/a (Line 4.1 / 2.1 x 0.5 x 100).3 Amortisation period Years 8.12 [Line 2.1 / (Line 4.1+Line 3.2)] Field test & market introduction The prerequisites for a field test and subsequent market introduction are fulfilled. Note: We wish to thank all those involved in the project for their assistance in the EU- LIFE program. LIFE99 ENV/D/