How you can make CHP score with a BREEAM assessment.
The internationally renowned Building Research Establishment Environmental Assessment Method for non-domestic and new constructions (BREEAM) was reviewed this year with significant changes in the energy category. The changes have implications for combined heat and power (CHP).
A high BREEAM assessment score gives you, the developers, designers and building managers, a credible demonstration of the environmental performance of your commercial or industrial buildings.
The new BREEAM assessment no longer specifies a level of renewable energy sources because that is addressed specifically in the latest building regulations. Reflecting this, the number of available BREEAM credits under carbon reduction has been reduced from 15 to 12 - shifting the weighting of energy impacts in BREEAM from 19% of the entire rating to 15%.
Credit where it’s due
A building’s energy performance rating under BREEAM is now calculated using the building regulations of the country where the building is located. This replaces the notional baseline used previously regardless of the building’s UK location.
BREEAM energy performance credits are based on a building’s heating and cooling energy demand, primary energy consumption and total carbon dioxide emissions – all areas where CHP can have an impact. These are compared with the relevant national building regulations baseline to give an Energy Performance Ratio (EPR). The calculation should be determined by an accredited energy assessor using software approved under the National Calculation Methodology for the relevant country:
Down to zero
BREEAM assessment credits for conducting feasibility studies for low and zero carbon (LZC) measures – which include CHP - fall under a new category: low carbon design. This is to ensure that a thorough review of LZC informs the building design at an early stage.
Where CHP is involved, an LZC study should include:
- Energy from the CHP.
- CHP carbon dioxide savings.
- CHP cost accounting for payback.
- Planning criteria, including land use and noise.
- Feasibility of exporting heat/electricity.
- Any available grants.
- All appropriate, optional energy technologies.
- Reasons for excluding other technologies.
- Where appropriate, connecting the proposed building to an existing local community source of heat or power.
- Specifying the CHP with the potential to export excess heat or power.
A heat map for the UK is available for this. More detailed maps are often available locally.
Pollution (Pol 02) - NOx Emissions Calculation Methodology
NOx emissions are pollutant gases which are formed by the combustion fossil fuels. These gases are considered hazardous to human health and the ecosystem. For the purpose of BREEAM, NOx emissions levels are required in units -mg/kWh and measured at 0% oxygen levels on a dry basis.
For CHP technology, it is only necessary to consider the heat-related nitrogen oxide (NOx) emissions towards the BREEAM pollution abatement score. The methodology determines the net NOx emissions from the CHP’s electricity generation compared with electricity generation from the grid and allocates this amount to the heat generation of the CHP, which is then compared with the benchmark scale.
Heat-related NOx in mg/kWhheat can be obtained by using the following formula:
(X) = (A - B) / C
X = NOx emissions per unit of heat supplied (mg/kWhheat)
A = NOx emissions per unit of electricity generated (mg/kWhelec) by the CHP Unit
B = NOx if the full load was emissions per unit of electricity supplied from the grid - 617 (mg/kWhelec)
C = Ratio of heat to electricity output of the CHP unit
Note: Where the value of ‘X’ is calculated to be negative, it should be assumed to be zero.
The heat-related component is then compared with the scale to determine the credit score.
Calculating NOx emission levels where CHP is operating is conjunction with other heating systems, an average NOx emission rate is to be used on the ratio or power output from each of the heating source, i.e. simply multiply the emissions of each system by the percentage of heat demand it supplies and then total these values. This is usually the case at most of the sites where the CHP system has been sized to meet the base energy (electricity/heating) demand and therefore a secondary system (usually boilers) is required. The following formula can be used for such cases:
Average NOx Emission Rate = (N1 x (H1/HT)) + (N2 x (H2/HT)) + …… + (Nn x (Hn/HT))
N1 = NOx emission rate for heat source 1
N2 = NOx emission rate for heat source 2
Nn = NOx emission rate for heat source n
HT = Total heat output from all sources
H1 = Heat Output from Source 1
H2 = Heat Output from Source 2
Hn = Heat Output from Source n
Assessment Criteria and Credit Allocations
|Building Types||NOx Emissions for heating and hot water (mg/kWhheat)||Credits|
|Non-industrial (all building types)||≤100||1|
|Non-industrial (all building types)||≤70||2|
|Non-industrial (all building types)||≤40||3|