The PV renewable calculation is carried out in the 'OnSite Gen' tab. DEAP supports up to five separate PV arrays, each of which may have a different orientation, tilt, and degree of overshading. The assessor must specify the following for each array:
The performance of PV modules should be taken from certificates from accredited laboratories testing to one of:
Test data for PV collectors may also be taken from SEAI’s Triple E product register. Triple E meets the PV test data criteria detailed above. If certified PV performance data is not available, the defaults in table 2 below must be used.
Where a battery storage system is present, the usable battery capacity in kWh should also be entered. The evidence required can be met by one of the following:
If data is not available to verify the battery storage capacity, then a default capacity of 2.4kWh should be used.
Guidance on re-use of data for Solar PV can be found here
Monthly electricity generation is calculated for each array by converting the horizontal solar radiation for that month to incident radiation on the inclined array surface. This conversion uses a transposition factor derived from the array's orientation and tilt, the site latitude, and the monthly solar declination. The incident radiation is then multiplied by the peak power, overshading factor, and a performance factor to give monthly generation. Where more than one array is present, monthly generation is summed across all arrays.
Monthly generation is then apportioned between electricity used directly within the dwelling and electricity exported to the grid. This split is determined for each month by comparing PV generation against total electricity demand (covering heating, water heating, lighting, appliances, cooking, pumps and fans), using a method that accounts for the statistical likelihood of generation coinciding with demand. Where battery storage is present, the effective self-use proportion is increased, since stored generation can be used later in the day. Where more than one on-site generation source is present, a correction is applied to ensure that combined self-use across all sources does not exceed total monthly electricity demand.
The primary energy factors and CO2eq emissions factors applied to both self-use and exported electricity are taken from Table 12.1 which can be found here in the results section.
The monthly electricity generation is calculated separately for each array. The monthly solar radiation incident on the array surface Sm is obtained by applying a transposition factor Tm to the monthly horizontal radiation Hm, using the same method as described in solar water heating with the orientation, tilt, and site latitude of the array. Monthly electricity generation for each array is then:
EPV,m = 0.8 × Sm × Zpv × kWp
where:
Where more than one array is present, the monthly generation figures are summed across all arrays to give total monthly PV generation.
At times of high solar radiation, the PV array may generate more electricity than the instantaneous demand within the dwelling. Monthly generation is therefore apportioned between electricity used directly within the dwelling (self-use) and electricity exported to the grid.
The monthly supply/demand ratio is:
R = EPV,m / Dm
where Dm is the total monthly electricity demand, covering pumps and fans, lighting, appliances, cooking, cooling, and any electrically driven space and water heating systems.
Where the main space heating system uses off-peak electricity, that component is excluded from Dm as it cannot be displaced by PV generation.
Three coefficients are derived from the usable battery storage capacity b (kWh), where b is capped at 15 kWh. Where no battery storage is present, b = 0:
CPV1 = 1.61 − 0.0973 × bCPV2 = 0.415 − 0.00776 × bCPV3 = 0.511 + 0.0866 × bThe monthly self-use proportion β is:
β = min(exp(−CPV1 × (R × CPV2)^CPV3), Dm / EPV,m) (M7)
The second term in the min() expression ensures that self-use cannot exceed total demand. Monthly self-use and export are:
EPV,self,m = EPV,m × βEPV,export,m = EPV,m × (1 − β)
In a building containing more than one dwelling where each dwelling has its own electricity supply and MPRN and the PV output is directly connected only to an individual dwelling's electricity supply, the annual output is credited to that dwelling only. An inverter is required for each dwelling with a PV electricity supply.
Where a number of self-contained dwellings share an electricity supply and MPRN, the PV output is divided between the dwellings in proportion to each dwelling's floor area as a fraction of the total floor area served by the PV system. Where common or landlord areas are connected to the same electricity supply, these areas must be included in the total floor area.
Note: This solution is limited to cases where all buildings are connected are dwellings and there are no commercial or non-domestic buildings connected to the same MPRN.
Note: Electricity supplied to common areas in a development is not considered in DEAP assessments. Where the PV system is used only for heating (for example directly wired to an immersion heater or storage heaters), the BER Helpdesk should be contacted for further guidance.
Table 8.1 - Overshading factors for PV
| Overshading | % of sky blocked by obstacles | Zpv |
|---|---|---|
| Severe | > 80% | 0.20 |
| Heavy | > 60% - <80% | 0.35 |
| Significant | > 40% - < 60% | 0.50 |
| Modest | > 20% - < 40% | 0.80 |
| None or very little | <20 % | 1.00 |
Table 8.2 - Default values for Peak Power
| Year of PV installation | Default kWp/m2 | Default kWp/Default panel1 |
|---|---|---|
| Up to 2010 | 0.060 | 0.090 |
| 2011-2015 | 0.090 | 0.135 |
| 2016 onwards | 0.120 | 0.180 |
1 Default area of 1.5 m2 per panel
If PV collectors are present, the data for unavailable parameters are set out here.