CHP plant for a leisure centre


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Measures to reduce the energy consumption have been suggested in a separate document. After the adoption of the ones that
the management thinks appropriate, the moment will be for the centre to think of a more economic and environmental friendly manner to generate its own energy.

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CHP plant for a leisure centre

  1. 1. 1 Alejo Etchart January 2009 A CHP PLANT FOR AYLESTONE LEISURE CENTRE 1. Background As seen in the technical report, Aylestone Leisure Centre’s energy consumption is well managed. Its annual consumptions are between a “typical” and a “best practice” leisure centre in electricity consumption, and better than “best practice” in gas consumption (a). Measures to reduce the energy consumption have been suggested in a separate document. After the adoption of the ones that the management thinks appropriate, the moment will be for the centre to think of a more economic and environmental friendly manner to generate its own energy. 2. A CHP for Aylestone Leisure Centre 2.1 Type of CHP Plant Combined heat and power (CHP) technology generates electricity on-site and utilises the heat necessarily produced as a by- product of the generation process. The figure on the left outlines the process for a 75% efficient plant. This way, it saves energy and reduces carbon emissions, by making the engine’s heat, which would otherwise be lost, available as hot water that can be used for space and water heating. Internal combustion (IC) engine plants are the most suitable for sizes around 100kWe (b). Gas Turbine and Steam Turbine plants are adequate for larger capacities. CHP is particularly suitable for sites occupied for at least 16 hours a day and with constant heat requirements, like swimming pools (c). This perfectly matches Aylestone’s case. Source: (b) 2.2 Sizing the CHP plant The capital investment in CHP plant is substantial, so it is important to target the plant size so that it operates as many hours as possible. This involves matching CHP capacity to base heat and power loads (d). Considering the electricity consumption of the last 52 weeks (930MWh metered), the proper size would be 100kWh (rounded down from 106.16). With the 90% efficiency that modern plants achieve (b), a 100kWh unit can generate 876MWh. The adoption of energy saving measures can reduce the energy needed; if not, the remaining amount must be covered by the grid. In any case, energy from the grid must remain available in order to overcome occasional insufficiencies in supply, and also to provide electricity during any maintenance down time (c).
  2. 2. 2 In this analysis, the efficiencies considered have been 40% for electricity and 50% for recovered useful heat. Therefore, the generation of 876MWh of heat will make available 1,095MWh of heat, almost covering the 1,100MWh consumed in the same period (see full calculations in footnote f ). Nevertheless, Action Energy provides for free the chpsizer2 software, a standalone tool that requires half-hourly data (already available for Aylestone L.C.) (e). 3. Economics With the assumptions made (shown in italics in the footnotes f), the investment on an IC engine CHP plant will involve the following economic performance: ANNUAL SAVING: £ 49,000 PAYBACK: 5.24 years DISCOUNTED CASH FLOW: £ 187,000 NET PRESENT VALUE: £ 928,000 INTERNAL RATE OF RETURN: 23 % Financial benefits The economic analysis has not taken into account the financing of the project. It will be of even further interest with these two benefits (d): 1. Enhanced Capital Allowance. It permits businesses to offset 100% of the capital cost of efficient CHP plants against tax in the first year, instead of having to spread the tax write- off over, say, 10 years. This can save around 7-8% of the capital cost over the plant life time. 2. Climate Change Levy exemption. Fuel input to good quality CHP qualifies for exemption from CCL, which can often reduce payback periods by 1-2 years. 4. Carbon emissions CHP has a lower carbon intensity of heat and power production than the conventional means, and this can result in a reduction of more than 30% in emissions of CO2, thus helping to reduce the risk of global warming. It will also reduce the emission of SO2, the major contributor to acid rain. The figure on the left shows a scheme of this comparison for a 80% efficient IC engine (d). 5. Further considerations 1. The economics and emissions above have been calculated assuming that the CHP will be run on natural gas. CHP installations can also run on bio-gas, gas oil or even biomass (d). When the CHP uses a locally available biofuel it can even be carbon neutral (c) 2. It is also possible to use for AC through chillers (c) 3. If the plant is oversized, the excess can be sold into the grid (c) 6. Conclusion
  3. 3. 3 By using a CHP plant, Aylestone L.C. will: - Reduce energy costs, compensating the investment in less than 5 years and delivering a 23% return on investment. - Minimise environmental emissions by 30%, helping the UK and Leicester to meet the emission reduction targets and fighting against global warming. - Improve security of electricity supply, covering potential drops from the grid. In the right application, CHP is the single biggest measure for reducing buildings related CO2 emissions and running costs (d). a Carbon Trust (2004), “ECG087- Energy use in local authority buildings” b Dr. Martin Smith (2008), DMU MSC CC&SD, EAT module, “CHP and the Climate Change Levy” c Carbon Trust (2005), “Building a brighter future”. Available at 9999F5A79284/0/Building_a_Brighter_Future.pdf (Accessed 24/01/09) d Carbon Trust (2004), “GPG388- CHO for buildings”, p.20 e CIBSE CHP GROUP e-Newsletter SEPTEMBER 2004, p.4 (Accessed 25/01/09) f CALCULATIONS AND ASSUMPTIONS Electricity meter: 930,000 kWh Gas meter: 1,100,000 kWh CHP Capital cost (*): 212,000 £ CHP Installation (20% cap.cost) (*): 44,944 (*): Estimations based on Thermie Worbook2 (1997, p.2.17), but double prece for the capital cost --> 2x1,000€/kW Electricity cost (**): 0.06 £/kWh Gas cost (**): 0.05 assumed 20% less (**): Only verbal estimations have been feasible without unavailable and confidentuial information CHP maintenance cost: 0.02 €/kWh Size kW rounded- calculated: 100.00 106.16 kW kWh CHP: 876,000 Residual value Years: 20 (15%): 31,800 Discount rate: 7% £/€ : 1.06 Power factor: 0.80 CHP Current electricity gas electricity gas boiler Efficiency 40% 50% 80% 65% Demand 876,000 1,095,000 930,000 1,100,000 Energy Cost 42,048 55,800 52,800 Maintenance cost 17,520 Annual energy saving -49,032 Payback years 5.24 Discounted cash-flow -187,017 Net Present value 927,640 Cash flow 1st year: -207,912 Cash flow 2nd-19th year: 49,032 Cach flow 20th year: 80,832 Internal Rate of Return 23%