Climate change legislation

Climate change legislation


Recent government climate change legislation has led to huge carbon reduction commitments being levied on all public sector organisations. The target of reducing carbon dioxide emissions by 80% by 2050 will require major changes in almost all aspects of an organisations operational function. CO2 is released into the atmosphere whenever fossil fuels are consumed and since currently almost every aspect of human existence relies to some point on fossil fuel the sea change that is required is vast.

The NHS must review all aspects of its operation, including procurement, transport, service delivery and the construction methods of its buildings to enable it to reach the carbon reduction targets set out by the UK government.

A major contributor to the total CO2 emissions of the NHS is the energy consumed by its buildings and occupants. The NHS carbon footprint in 2004 was 18.6 Mt CO2. This represents 25% of England's public sector emissions. 22% of the NHS emissions, (4.14MtCO2­) were from building energy.

This document will evaluate the potential for reducing the carbon emissions of an existing NHS site taking into account the potential for reducing energy consumption and the use of onsite renewable technologies. Potential pay back periods will be evaluated; however these are difficult to calculate as the energy markets will almost certainly be very different in future years.

Rubery Site

Formerly the Rubery site was occupied by Rubery Hill Hospital, a large Victorian psychiatric hospital with xx beds. In 1990 Reaside Clinic was opened providing medium secure psychiatric care to 90 patients. In 1995 Holly Hill Nursing home was opened providing long term inpatient psychiatric care to 50 elderly residents. Following the opening of Holly Hill Nursing Home the original Rubery Hill Hospital was closed and demolished. Holly Hill nursing home was constructed with gas fired LPHW heating and direct gas fired water heaters. Until Rubery Hospital was demolished, the primary heat source for the Reaside Clinic was the main hospitals coal fired steam raising boiler house containing xxxx boilers. Steam at xx bar was fed to heat exchangers within the clinics first floor plant room, providing the heat source for domestic hot water and a conventional LTHW heating system.

When the main hospital closed the coal fired boiler house was decommissioned and demolished. There were a number of options available to provide heat and hot water to Reaside Clinic, one of which involved installing new LTHW boilers in the first floor plant room, however the space is limited and there was no nearby suitable gas supply to feed the boilers. The preferred option was to install a containerised steam raising boiler room in the service yard and connect onto the existing steam mains. This was considered to be the most cost effective solution as much of the existing plant including the heat exchangers and water storage vessels would be able to remain.


Reaside Clinic and Holly Hill nursing Home located on the Rubery site are supplied by mains natural gas and mains electricity from the grid network. Import energy consumption information for the two buildings has been obtained for the calendar year 2009. The buildings have been operating with very similar patient and staff numbers since their construction in 1990 and 1995. The year 2009 will be used as the benchmark consumption by which all energy reductions and generation technologies will be measured. In the absence of sufficient metering, calculations and assumptions will be used to determine the energy profile of the buildings, i.e how much of the imported energy is used to heat the space and how much heats the hot water etc. The energy consumptions will be compared to other similar establishments in the NHS and private sector. A comparison will be made with buildings constructed to the latest energy efficiency standards to determine by what amount the CO2 ­­­emissions will be reduced by replacing the buildings with ones constructed to current standards.

To meet the UK government's target of 80% reduction in CO2 emissions by 2050 it is clear that by constructing more energy efficient buildings alone will not be sufficient. There will have to be an amount of the buildings energy needs met by low or zero carbon technologies. Low and zero carbon technologies will be appraised for their suitability and cost effectiveness for providing energy to inpatient healthcare establishments where security of supply is essential for patient safety.

As the two buildings are within 250 metres of each other, share a common site and are operated by the same NHS organisation, the investigation will include the possibility of interconnecting the systems to increase efficiencies and costs

Ultimately the aim is to suggest a suitable energy source that is commercially viable, sustainable and practical for the site which will reduce the carbon emissions associated with building energy by at least 80%

Climate Change Legislation

It is widely accepted amongst the world's Scientists that human civilization is affecting the world's climate. The gasses in the earth's atmosphere are in a delicate balance. The amount of carbon dioxide in the atmosphere is small only 0.039% however the CO2 plays an important part in the climate balance of the planet. Sunlight passes through the atmosphere as visible light with a short wave length. The sunlight heats the surface of the planet which then emits longer wavelength infra red radiation. This infra red radiation is trapped by the CO2 in the atmosphere causing the atmosphere to warm up. Without this effect the planet would be much colder; however research has concluded that the CO2 levels in the atmosphere are reaching dangerously high levels causing long term changes to the planets climate. Man's consumption of fossil fuels over the last 100 years has led to the release large amounts of CO2 ­­ into the atmosphere. The first studies into CO2 concentrations in the atmosphere were conducted by Charles David Keeling at the Scripps Institution of Oceanography in La Jolla, California. The Scripps CO2 ­ programme was initiated in 1956. The graph below shows that the concentration of CO2 has risen from about 315 ppm (parts per million) to 385 ppm.

The United Nations Framework Convention on Climate Change (UNFCCC) was produced at the United Nations Conference on Environment and Development known as the Earth Summit which was held in Rio de Janeiro in June 1992. The treaty was set up to consider how to reduce global warming and to cope with the temperature increases that seem inevitable. On the 11th December 1997 the Kyoto protocol was adopted. This came into force in 2005 setting legally binding emissions limits for all participating countries. These legally binding emission limits have led to the current European and UK legislation in force today.

The UK Climate Change Act 2008 forms the legal framework for The UK Low Carbon Transition Plan. The plan sets out how all aspects of life in the UK will have to adapt if the country is to achieve its ambitious target of 80% reduction in net Carbon Dioxide emissions by 2050

(1)It is the duty of the Secretary of State to ensure that the netUKcarbon account for the year 2050 is at least 80% lower than the 1990 baseline.

(2)“The 1990 baseline” means the aggregate amount of—

(a)net UK emissions of carbon dioxide for that year, and

(b)net UK emissions of each of the other targeted greenhouse gases for the year that is the base year for that gas

Reaside Clinic- 2009 Energy Profile

Reaside Clinic is an inpatient mental health clinic with 90 individual bedrooms across 7 wards. The building has two floors across the majority of the site, the facilities section being single storey. The building has a gross internal area 7084m­­2. The gross internal volume is 19126m3.­ A floor plan of the building is located in appendix 1f.

Construction Details

The building was constructed in 1990. Wall construction is detailed in appendix 2, consisting of 100mm outer brick, 50mm cavity insulated with fibre glass wool, the inner wall being medium density concrete block. Interior surfaces are directly plastered. The windows throughout are double glazed units in powder coated aluminium frames. There is tiled cold roof construction across the whole building.

Import Energy Metering

Total consumed energy can be calculated from the site gas and electricity import meters.

The site natural gas consumption is measured in cubic metres which are converted in to an energy value. The calorific value of the gas supplied is quoted by the supplier on each monthly invoice. A pressure correction factor is applied to convert the metered volume of gas into the same pressure and temperature as the base pressure and base temperature used to calculate the calorific value.

The kilowatt hours of energy supplied =

kWh = Volume(M3) x calorific value (MJ/M3) x Pressure correction factor ÷ 3.6

The consumed electricity is directly read from the meter.

The most recent gas and electricity meter readings available are for the 2009 calendar year. The total gas consumed was 2,509,984 kWh, the total electricity consumption being 1,095,725 kWh. The total energy consumed in 2009 was 3,605,710 kWh. When calculating the energy efficiency of buildings, the convention is to use a measurement of giga joules per 100m3 per year. Using the consumption data this figure is 65.44 GJ/100m3 per year.

There is insufficient metering on the site to be able to determine the ratio of how much heat energy is used to provide the heating compared to domestic hot water and how much electrical energy is used by the fixed equipment of the building e.g. lighting, plant and machinery and how much electricity is used by the occupants i.e. computer equipment. This will be determined by assumption and reasoned argument.

Gas Consumption

Gas is consumed on site by the main heating boilers which provide heating and domestic hot water and the kitchen cooking appliances. The gas consumption for the main kitchen is measured by a ‘sub' meter. The kitchen consumption can be subtracted from the overall site consumption which will show how much energy is used to provide heating and hot water. As the measurement is for heat energy input into the systems, all plant losses are included.

If it is assumed that the building is fully occupied all year round, the domestic hot water consumed will remain constant. The losses in the domestic hot water circulation will be constant as all pipe work is contained within the building at a fairly constant temperature. It can also be assumed that the losses attributable to the steam generation and transportation will remain constant throughout the year as the steam mains are located in ducts within the building and will also be at a constant temperature throughout the year.

The major variable in the gas consumption will be the heating load. The building is controlled by a BMS computer which keeps the ward areas at 21°C all year round. (There is no night set back as psychiatric patients are awake at irregular hours). The admin areas are heated to 21°C during office hours and are allowed to fall back to 16°C overnight and on weekends. The heating load will be proportional to the external temperature.

The gas consumption figures show that the monthly gas consumption peaked in January 2009 at 382914kWh. The minimum gas consumption was in July 2009 at 82365 kWh (21%) of the peak monthly usage.

The mean daily temperatures for 2009 are shown in appendix 1d.

Reaside Clinic Carbon Dioxide Emissions

The carbon dioxide emissions that are directly attributable to the energy consumed are determined by applying multiplying factors to the imported energy. The factors have been calculated to include the carbon dioxide emissions in obtaining or generating the energy source.

The CO2 released when burning natural gas can be calculated from the chemical reactions taking place when the constituent gasses are burnt in air; however there is an additional amount of energy used and therefore CO2 emitted in extracting the natural gas from the underground reserves and pumping it to the point of use. When natural gas is removed from the ground it contains mainly methane but will have small amounts of butane, propane and other non combustible gases such as CO2 and sulphur dioxide. These gasses are removed before the gas is pumped to the consumer, butane and propane being liquefied and used as a fuel. This processing of the fuel uses energy and causes the release of more CO2 into the atmosphere.

The CO2 released when using electricity takes into account all of the different generation types, oil, coal, gas, nuclear, hydro electric etc and the conversion and transmission losses associated with delivering the supply to the end user, however when using electricity from the grid, no CO2 is actually released at the point of use. Due to a large proportion of electricity in the UK being generated in coal fired power stations with relatively low overall efficiencies the CO2 emission factor for grid supplied electricity is the largest for any fuel type.

The CO2 emission factors are shown below in table 1.1. This is an extract from The Building Regulations Approved Document L2A 2000 (2006 version). The CO2 emissions from grid supplied electricity are calculated by The Department for Environment, Food and Rural Affairs (DEFRA), and are presented as a 5 year rolling average. The factor for grid supplied electricity alters because the landscape of electricity generation in the UK is changing. Inefficient coal fired power stations are being decommissioned and more renewable sources such as wind are coming on stream. The predicted electricity emission factor for 2020 is 0.45

Table 1.1CO2 Emission Factors


CO2 ­Emission Factor kgCO2/kWh

Natural gas












Smokeless Fuel Inc Coke


Dual Fuel Appliances (mineral & wood)




Grid Supplied Electricity


Grid Displaced Electricity­­1


Waste Heat2



1. Grid displaced electricity comprises all electricity generated in or on the premises for instance, PV panels , wind powered generators, combined heat and power (CHP) etc. The associated CO2 emissions are deducted from the total CO2 emissions for the building before determining the BER. CO2 emissions arising from fuels used by the building's power generation system(e.g. to power the CHP engine must be included in the building CO2 emissions

2. This includes waste heat from industrial processes and power stations rated at more than 10 MWe and with a power efficiency >35%

Using the total 2009 energy consumption figures in appendix 1a and the emission factors from approved document L2A the total CO2 emissions for the Reaside Clinic are:

Natural Gas:

2,509,984 kWh x 0.194 kgCO2/kWh= 486936kg CO2 = 486.9 tonnes CO2


1,095,726 kWh x 0.422 kgCO2/kWh= 462396kg CO2 = 462.3 tonnes CO2

Total effective CO2 output =949.2 tonnes

This figure of 949.2 tonnes will be considered as the benchmark figure by which the 80% reduction is required.

Holly Hill Nursing Home - Energy Profile

Holly Hill Nursing Home was constructed in 1995 and provides inpatient accommodation for 30 elderly psychiatric patients. The building is single storey throughout and has an administration block attached. The whole building is heated to 23°C 24 hrs per day. There are 30 patients and 12 to 20 staff in the building. The admin section has accommodates 15 office staff.

Food is not cooked on site. A cook-chill-reheat process is used. Domestic hot water is provided by the main heating boilers through a heat exchanger and stored in 2 x 500 litre calorifier vessels. The domestic hot water usage is not measured.

Building Construction Details

The building is constructed from prefabricated 'pods' having a 100mm outer brick skin. The roof is a pitched cold roof construction. Nett internal floor area is 1600M2. The nett internal volume is 4320M3. The building has double glazing throughout. Two 100kW gas fired boilers provide heating through a LTHW system comprising of conventional low surface temperature radiators in each room.

Energy Metering

The building has an import gas meter measuring cubic metres and an import electricity meter directly reading import kilowatt hours. Gas and electricity import meter readings are available for the 2009 calendar year (shown in appendix 1c)

The total import energy for 2009 was 665,971kWh

665,971kWh x 0.0036=2397.4GJ

2397.4÷4320=0.555GJ/M3 or 55.5GJ/100M3

Using the total 2009 energy consumption figures in appendix 1a and the emission factors from approved document L2A the total CO2 emissions for the Holly Hill Nursing Home are:

Natural Gas:

496,651 kWh x 0.194 kgCO2/kWh= 96286kg CO2 = 96.3 tonnes CO2


169,320kWh x 0.422 kgCO2/kWh= 71453kg CO2 = 71.4 tonnes CO2

Total effective CO2 output =167.7 tonnes

This figure of 167.7 tonnes will be considered as the benchmark figure by which the 80% reduction is required.

Energy costs at January 2010 prices are.

Gas- £0.028 per kWh £84185.78

Electricity - £ 0.084 per kWh £106263.86

Total energy spend in 2009 £190448.78

Meeting the Requirements of:

The Climate Change Act 2008

The Climate Change Act 2008 requires that the nett carbon emissions of an organisation are reduced by 26% from the 1997 baseline by 2020 and 80% from the 1997 baseline level by 2050. The NHS has a carbon footprint of 18M tonnes CO2 per year see table 2.1 below for a breakdown.

Table 2.1



3.24 M tonnes CO2

Building Energy


3.96 M tonnes CO2



10.8 M tonnes CO2


18 M tonnes CO2

It is clear that with building energy use amounting to almost a quarter of the overall NHS CO2 emissions major investment is required in this sector to achieve the 80% reduction required by UK law.

The Options for the Rubery Site.

Option 1 Rebuild

Currently Reaside Clinic has an energy efficiency of 65.44 GJ/100M3 and Holly Hill Nursing Home has an energy efficiency of 55.5 GJ/100M3. Total annual CO2 emissions for the site are 1117 tonnes per year. To achieve the targets set out by the Climate Change legislation the overall site emissions will have to reduce to 849 tonnes by 2020 and 223.4 tonnes by 2050.

A reduction of this scale is a huge undertaking. Current healthcare building projects are required by the NHS to achieve BREEAM ‘excellent' standards in energy efficiency having overall energy consumption lower than 35GJ/100m3. This efficiency rating will only be achieved by a complete rebuild of both buildings costing in excess of £15million for Holly Hill Nursing Home and £25 Million for Reaside Clinic.However having spent £40 million pounds constructing buildings with the best efficiencies currently available, will these buildings meet the 2050 CO2 reductions. Assuming that grid supplied gas and electricity are the main fuels the projected CO2 emissions are shown below.

Reaside Clinic 2009 energy split electricity 30%, Gas 70%

Holly Hill 2009 energy split 25.4% Gas 74.6%

Assuming the new buildings are much more thermally efficient than the existing buildings, a gas / electricity split of 50/50 is a more appropriate figure to use.

Reaside Clinic & Holly Hill Gross Volume

23446m3 x (35/100) = 8206 GJ x 277.78 = 2,279,444kWh

Assuming 50/50 split = 1,139,722kWh Gas & 1,139,722 kWh electricity

Gas CO2 emission factor =0.194 kg CO2 /kWh

Grid connected electricity CO2 emission factor 0.423

Natural Gas CO2 emissions 1,139,722x 0.194=221106kg

Electricity CO2 emissions 1,139,722x 0.423=482102kg

The predicted total CO2 emissions are 703.2 tonnes per year against a benchmark 2009 figure of 1117 tonnes. This is a 37% reduction which will satisfy the 2020 reduction target but not the 80% by 2050.

CO2 reduction over 2009 baseline figure

414 Tonnes CO2 or 37% of the baseline 2009 (949.2 tonnes)

Cost per tonne CO2 per annum=£96,618 per tonne per year

Cost per 1% reduction in CO2 £162,162

Option 2 Renewable Sources (On site Generation)

In an ideal world the NHS would commit to replacing all of its underperforming buildings with modern energy efficient constructions; however the cost to the UK taxpayer would be vast and unaffordable. An alternative approach to reducing CO2 is to use forms of energy that emit less CO2 or ideally none at all.

The technologies employed are called ‘Renewable Sources' but a more accurate description would be ‘Low and Zero Carbon' (LZC) technologies.

The most commonly used low and zero carbon energy sources available are:

Solar Power

o Solar Photovoltaic

o Solar Thermal


Small Scale Wind Turbines

Biomass and Bio Fuels

Biomass / Bio Fuel Boilers

Combined Heat and Power (CHP) using the following Fuels:

  • Biomass
  • Natural Gas
  • Biogas
  • Bio Diesel

Heat pumps

  • Ground source heat pumps
  • Water source heat pumps
  • Geothermal heating systems
  • Air source heat pumps

Stage 1: Reduce Current Energy Demand

The current energy demand of the 2 buildings is very high compared to the energy efficiencies of modern ‘BREEAM Excellent' rated buildings. Whilst complete reconstruction will currently be out of the question due to the re-build costs, significant energy saving measures can be used to reduce the energy demand.

The space heating load can be reduced by improved air tightness and heat recovery systems. The windows could be replaced with units having a much higher thermal efficiency. Electrical load can be reduced significantly by the use of more energy efficient lighting combined with proximity detection to prevent areas being illuminated when there is no requirement to do so. The electrical equipment used by the building occupiers, i/e. PC's, photocopiers etc. can be replaced with low energy machines. Insulation of the building fabric can be improved where possible. Roof space insulation can be relatively easily improved, significantly reducing the amount of heat energy lost from the building envelope.

A conservative estimate is that the energy consumption of the site could be reduced by 20% over the 2009 benchmark figure.

2009 Gas Heat energy input =3,006,6351kWh

Assuming existing boilers and plant are 75% efficient, actual heat energy used for space heating and hot water =2,254,976 kWh.

20% efficiency savings =1,803,981kWh heat energy required.

Electrical energy imported in 2009 =1,265,046kWh

20% efficiency savings= 1,012,036kWh

Solar Power

Solar Power is produces no carbon dioxide or other polluting emissions as it produces energy. Solar systems use the power of sunlight to generate electricity directly - solar photovoltaic (Solar PV) or to generate heat - solar thermal.

Solar PV

Photovoltaic panels are manufactured from silicon cells which generate electricity when light illuminates the cells. Efficiencies of 25% have been achieved in experiments; however currently mass produced cells achieve efficiencies of about 18%. Simply this means that 18% of the energy in the sunlight is converted into electricity. Electricity generated from solar photovoltaic cells cannot be easily stored meaning that the energy is only available during daylight hours. The energy produced by solar photovoltaic panels is proportional to the amount of light energy falling on the earth's surface. Figure 1 shows the annual amount of solar energy irradiating the earth's surface in Europe. The figure shows that typically in Birmingham, England about 1100 kWh falls on every m­2 of the earth's surface every year. Commercial PV systems with a performance ratio of 0.8 will produce approximately 800kWh per year per m2. Electricity from solar photovoltaic systems cannot be relied upon as a primary source of energy as solar PV cells require direct sunlight to produce the maximum rated power, sunlight that is shaded by cloud restricts the output and no power is generated during the hours of darkness.

Solar PV is currently very expensive to install, typically systems cost £6000per kW peak to install. Assuming a performance ratio of 0.8 each m2 installed will generate 800kWh pa. System life is typically 30 years; however maintenance costs will be low.

Each m2 of installed panel will produce approx 24000 kWh of electricity over its installed life.6000/24000=25 pence per kWh. This does not take into account the cost of financing the initial investment. If the finance costs are taken into account the price per kWh will be more like 30 pence per kWh which is approximately 2.5 times the current connected supply price.

As previously shown the site electricity consumption would be about 1,012,000kWh following energy efficiency measures. 80% of this demand could be met by installing 1000kW peak of generation capacity producing around 800,000 kWh per annum at an estimated cost of £6 million.

The maximum electrical demand of the buildings on the Rubery site is around 70kVA. If 1a 1000kW peak solar PV installation was installed, on the brightest summer days over 90% of the electricity produced would have to be exported to the electricity grid, being sold to the supply company. Effectively the electricity supply grid is used a storage system where the electricity is exported when the demand is lower than the amount produced, and imported when the demand is higher than produced. i.e at night or in the winter.

It must be noted that the manufacture solar PV panels currently uses large amounts of energy, unless the PV panels are constructed using low or zero carbon energythey have a high level of ‘embedded carbon'; however the embedded carbon is not taken into account by the BREEAM assessment.

CO2 reduction over 2009 baseline figure

800,000 kWh of solar PV electrical energy displaces 800,000 kWh import grid electricity with a CO2 emission factor of 0.422.

800,000 x 0.422 = 337.6 Tonnes CO2 or 30.2% of the baseline 2009 (1117 tonnes)

Cost per tonne CO2 per annum=£17,772 per tonne per year (£6,000,000 install cost)

Cost per 1% reduction in CO2 £198,675

Cost Per kWh over life of system (30years) £0.25 (not including maintenance or interest costs)

Solar Thermal

When the sun's rays strike the earth's atmosphere the light is scattered to a greater or lesser degree depending upon the cloud cover. The scattered light comes to earth in the form of diffuse radiation which gives the appearance that light comes from all over the sky. Without diffuse radiation the sky would appear black. Direct radiation is light that appears to come directly from the sun. In North Western Europe, on average over the year approximately 50% of the solar radiation is direct and 50% is diffuse.Both direct and diffuse solar radiation can be used for solar thermal applications.

As we have seen with the photo voltaic systems there is approximately 1000kWh/m2 energy falling on the surface of the UK over a year. The quantity of energy useful falling on the earth's surface in the UK varies considerably during the year. The maximum amount of energy falling on a horizontal surface is around 5kWh per m2 per day. In January this figure is around one tenth of the July maximum. The consequence of this is that the solar thermal energy is primarily available for systems that require heat in the summer, with much less energy being available in the winter.

The most efficient solar thermal collectors use evacuated glass tubes containing flat plates covered in light absorbing material. The sunlight passes through the glass tube and lands on the collector inside. Energy from the sunlight causes the collector to heat up. This energy is transferred via conduction to a medium

Costs for installed solar thermal systems are around £2000 per square metre of installed panel on large scale installations. Annual yield for the evacuated tube type solar thermal collectors is around 650kWh per m2.

To make use of all of the energy generated by a solar thermal system it be sized for the thermal load required at the time of year that it generates maximum power. A major problem with solar thermal generation is that the system will generate the maximum amount of heat at a time when the load is at its lowest. Assuming a 90% conversion factor, maximum power output will occur in July (Insolation data in table xx) where an expected energy yield would be 4.55 x 0.8= 3.64kWh per m2

Table xx

Monthly Averaged Insolation Incident On A Horizontal Surface (kWh/m2/day)

Lat 52

Lon -3













22 Year Average













Site thermal demand in July is 50,000 kWh over 31 days

Installed capacity required to meet demand 50,000÷ (3.64x31) = 443 m2

Assuming an installed cost of £2000 per m2 = install cost of £886,000

Expected system life = 30 years.

Annual yield at 650kWh per m2 = 650x443=287,950kwh

Cost per kWh over 30 years = 886,000 ÷ (287,950x 30)= £0.10 per kWh

CO2 reduction over 2009 baseline figure

287,950 kWh of solar thermal energy displaces 383,933 kWh import Natural gas with a CO2 emission factor of 0.194.

383,933 x 0.194 = 74.483 Tonnes CO2 or 6.6% of the baseline 2009 (1117 tonnes)

Cost per tonne CO2 per annum=£11,893 per tonne per year (£886,000 Install Cost)

Cost per 1% reduction in CO2 £132,242

Cost Per kWh over life of system (30years) £0.103 (not including maintenance or capital costs)

Wind Power

Electrical power can be generated on site using the force exerted by the wind to drive a turbine connected to an electrical generator. No fuel is ‘burnt' in generating the electrical energy produced by wind turbines therefore no CO­­2 is released on site.

In recent years, ‘farms' of large wind turbines have been constructed in areas where wind speeds are consistently high, usually on coastal hills or off shore. Large wind turbines are usually rated at 1MW but can be up to 4MW capacity. 1MW wind turbines typically have rotor diameters of about 60m. The largest wind turbines are currently using rotors in excess of 120 m in diameter.

Small wind turbines (SWT's) are classed as turbines with a generating capacity from below 1kW to 100kw (see table xx)

Table xx Classification of Small Wind Turbines

Rated Power kW

Rotor Swept Area (m2)

Sub Category

Prated <1kW



1kW< Prated<7kW

A<40 m2


7kW< Prated<50kW



50kW< Prated<100kW


(No clear Definition adopted yet)

The annual yield of a SWT will be affected by the frequency and amount of wind available. The yield will also be affected by the terrain surrounding the turbine.

At high levels, over 1000m the wind is not influenced by the surface of the earth; however at low levels the roughness of the terrain affects the wind speed. Friction against the surface of the earth will slow the wind. In rural locations, tall trees and forests will slow the wind speed. In cities the wind is slowed down by the irregular shapes of the buildings. The wind speed around a turbine can be affected by terrain up to 10km away although the farther away the obstruction or higher roughness, the less significant the effect on the wind speed. The Department of Energy and Climate change have produced a database of average wind speeds for locations in the UK. Average wind speed data for heights at 10m, 25m and 40m above ground level can be returned by entering the Ordinance Survey coordinates.

Wind Speed database Query Results (Ordinance survey Coordinates SO99477)

Wind Speed at 45m agl (m/s)


Wind Speed at 25m agl (m/s)


Wind Speed at10m agl (m/s)


Use of manufacturers data and the average wind speed will produce an expected energy yield for a given turbine size and pylon height.

Sample data below is for a turbine with a 133m2 swept area mounted at 18m above ground level.

Figure xx Power Output of Small Wind Turbine

The manufacturer's data predicts an annual yield of 31,293 kWh assuming a mounting height of 18m and an average wind speed of 5m/s.

Small Wind Turbines will not be able to provide continuous power for a site. There is intermittency to the wind speed which will cause fluctuations in the amount of power generated. There will be a minimum wind speed at which the turbine cannot overcome the resistance of the generator and will not turn. There is also a maximum wind speed beyond which the turbine would not be safe to operate. The automatic monitoring controls will detect when the wind speed is beyond limits and will apply a brake to stop the turbine.

Electronic controls will ensure that the output of the turbine is of the correct voltage and frequency to be ‘synchronised' with the site mains supply.

Major disadvantages of wind turbines are the noise created by the turning blades and the visual impact of large structures obscuring the landscape.

Sound power level emitted from wind turbines will be in the region of 90-100dB(A), which will create a sound pressure level of 50-60dB(A) at 40m. At 500m the sound pressure level will be 25-35dB (A) down wind and 10dB lower upwind.

The most significant risk to a SWT installation will be getting the required planning approvals for the turbines. The proximity to residential housing will be a major factor. Proximity to aviation routes may also be prohibitive.

Costs for a single 133m2 wind turbine on an 18m pylon would be around £45,000 plus the cost for the foundations (£8,000 each turbine). Assuming there are six such turbines installed across the site. Total cost is £318,000

CO2 reduction over 2009 baseline figure

187,000 kWh of wind generated electrical energy displaces 187,000 kWh import grid electricity with a CO2 emission factor of 0.422.

187,000 x 0.422 = 78.9 Tonnes CO2 or 7.1% of the baseline 2009 (1117 tonnes)

Cost per tonne CO2 per annum=£4030 per tonne per year (£318,000 install cost)

Cost per 1% reduction in CO2 £44,788

Cost Per kWh over life of turbine (20years) £0.06 (not including maintenance or interest costs)

Medium Sized Wind Power

To install a medium sized wind turbine would require a full consultation exercise with the Planning Authority and the local residents; however the amount of electrical energy that it would be possible to produce using one such machine is high relative to the SWT and is worth investigating.

A 30m diameter unit mounted at 30m hub height would produce approximately 400,000 kwh per year at an installation cost of approximately £500,000. The installation cost will vary depending upon the ground conditions and the size of the concrete base required. Working life of large wind turbines is quoted by the manufacturers as exceeding 20 years.

CO2 reduction over 2009 baseline figure

400,000 kWh of wind generated electrical energy displaces 400,000 kWh import grid electricity with a CO2 emission factor of 0.422.

400,000 x 0.422 = 168.8 Tonnes CO2 or 15.1% of the baseline 2009 (1117 tonnes)

Cost per tonne CO2 per annum=£2962 per tonne per year (£500,000 install cost)

Cost per 1% reduction in CO2 £33,112

Cost Per kWh over life of turbine (20years) £0.06 (not including maintenance or interest costs)

Biomass and Bio Fuels

Biomass fuel is created when the energy of the sun and carbon dioxide from the atmosphere are combined during the process of photosynthesis in plant life. These plants can subsequently be consumed by animals to produce animal biomass.

If the plant material is not eaten by animals it is generally broken down by micro organisms releasing carbon dioxide and methane back into the atmosphere.

This process is known as ‘the carbon cycle'. By harvesting the biomass in its many forms and burning it to generate heat, the same carbon cycle is maintained. If the biomass source is managed, i.e. the harvested plants are replanted and grown again; the cycle is ‘carbon neutral'.

The process of managing the growing crop, harvesting, processing and delivery to site currently is carried out using machinery and processes powered by fossil fuels. Consequently biomass fuels are not true zero carbon but will have a small CO2 emission factor. Typically this value is 0.026 kgCO2 per kWh.

A significant factor to be considered when evaluating the use of biomass fuel is storage of the fuel supply. To enable the fuel to be burned efficiently it must be stored correctly and not allowed to absorb additional moisture. The size of the storage facility required will depend upon the load of the system and the frequency of delivery. Table xx below shows the calorific value of the two most commonly available types of biomass fuel. Wood pellets are manufactured by compressing wood shavings and sawdust into uniformly shaped and sized pellets. No added chemicals or bonding agents are used in the process. Wood chips have higher water content and are of non standard composition. Wood chips consist of irregular chippings from sawmills and the forestry industry an can be in the region of 5 to 50mm in size.


Wood Pellets

Wood Chips

Calorific Value

17.0 GJ/t

13.4 GJ/t

Per kg

4.7 kWh/kg

3.7 kWh/kg

per m3



Water Content






Ash Content (% of mass)



Cost per tonne(2010)



Assuming a delivered heat requirement of 2,254,976kWh, the amount of biomass fuel required per annum can be calculated from the details in table xx. A boiler efficiency of 85% can be assumed. Total heat required is 2,819,000 kWh per year.

To deliver this amount of heat energy will require 599,727 kg of wood pellets or 761,891 kg of wood chips. Typical capacities of delivery vehicles will be 8 tonnes of wood chips or 10 tonnes of wood pellets. Annual delivery vehicle movements will be 60 deliveries of wood pellets or 95 deliveries of wood chips.

In January 2009 the peak gas consumption for the site was 454,829kWh, with a delivered energy of 341,121kWh. To meet this demand, the biomass fuel consumption would be (assuming 85% efficient boilers) 72.5 tonnes of wood pellets of 92.2 tonnes of wood chips requiring 8 deliveries of pellets or 12 deliveries of wood chips.

NHS guidance requires that a minimum of 20 days' supply is stored to ensure continuity of supply in case of extreme circumstances. This will require a storage silo with a 46 tonne capacity (70m3) if wood pellets are used or 60 tonne capacity (300m3) if wood chips are used.

Currently (March 2010) fuel costs for wood pellets which are sourced from sustainable UK forest are £210 per tonne. Wood chips are £110 per tonne.

Costs for installing biomass boiler and associated feed equipment are currently £478 per kW of boiler capacity. The heat demand will require 1MW of installed capacity

CO2 reduction over 2009 baseline figure

2,819,000 kWh of biomass heat with a CO2 emission factor of 0.025 displaces 3,006,635kWh import natural gas with a CO2 emission factor of 0.194.

3,006,635 x 0.194 = 583.3 tonnes CO2 (Gas)

2,819,000 x 0.025= 70.5 tonnes CO2 (Biomass)

CO­2 reduction =512 tonnes or 45% of the baseline 2009 figure (1,117 tonnes CO2)

Cost per tonne CO2 per annum=£934 per tonne per year (£478,000 install cost)

Cost per 1% reduction in CO2 £10,622

Wood Chip

Cost Per kWh over life of boiler plant (15years) assuming wood pellets at 2009 prices:

Fuel Costs (15x 2,819,000) ÷3.7 = 11428 tonnes of fuel@ £110 per tonne

= £1,257,121 + Capital Cost £478,000 =£1,735,121

Cost per kWh =£0.041

Wood Pellets

Cost Per kWh over life of boiler plant (15years) assuming wood pellets at 2009 prices:

Fuel Costs (15x 2,819,000) ÷4.7 = 8996.8 tonnes of fuel@ £210 per tonne

= £1,889,328 + Capital Cost £478,000 =£2,637,328

Cost per kWh =£0.055

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