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.

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
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
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
http://www.carbontrust.co.uk/NR/rdonlyres/A89DB6C2-9AE7-4450-BC24-
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
http://www.cibse.org/pdfs/CHP%20Group%20newsletter%202.pdf (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%