Z E M C H 2 0 1 2 I n t e r n a t i o n a l C o n f e r e n c e
628
Electricity generation using PV system with the roof tilt of 30
o
Avg. electricity required per month = 602.88kWh Avg. PV generated electricity per month =
250kWh
Electricity demand that is not supplied by PV = 602.88 kWh - 250 kWh = 352.88kWh per month
(a) Cost of electricity bought from the grid = 352.88kWh x £0.14 = £49.40 per month
(b) Cost of electricity saved = 250kWh x £0.14 = £35 per month
(c) Amount earned from the generation of PV electricity = 250kWh x £0.21 = £52.50 per
month
Potential earnings from PV generated electricity = b + c - a =
£38.10
per month
(£457.20/year)
Table 3: Earning from 100% use and 0% export of PV generated electricity through FIT scheme
Electricity generation using PV system with the roof tilt of 30
o
Avg. electricity required per month =
602.88kWh
Avg. PV generated electricity per month =
250kWh
Energy exported to the grid (50% of generated) = 125kWh per month
Electricity demand that is not supplied by PV = 602.88 kWh - 250 kWh = 352.88kWh per month
(needs to be bought from the grid)
But as 50% of electricity generated is exported to the grid, electricity to be bought = 352.88kWh +
125kWh = 477.88kWh per month
(a) Cost of electricity bought from the grid = 477.88kWh x £0.14 = £66.90 per month
(b) Cost of electricity saved = 125kWh x £0.14 = £17.50 per month
(c) Amount earned from the generation of PV electricity = 250kWh x £0.21 = £52.50 per
month
(d) Amount earned from the 50% export of PV generated electricity = 125kWh x £0.03 =
£3.75 per month
Potential earnings from PV generated electricity = b + c + d - a =
£6.85 per month
(£82.20/year)
Table 4: Earning from 50% use and 50% export of PV generated electricity through FIT scheme
When PV thermal energy is also considered as a source applied to the operation of a
house (e.g. for space heating), the economic gains from the use of PV/T system can
also be expected. The existing house observed was heated by a mains gas combi-boiler;
accordingly, the retail price of mains gas, i.e. £0.04/kWh, should be used for the estimate
(Scottish Hydro 2012). When the potential thermal energy production from PV is
considered to be 3,440kWh/annum (Table 2), the total earnings from the PV thermal
energy contribution can equate to £137.60/annum (Table 5). When 100% of PV heat can
be used, the economic value can be added to the expected earnings gained from the PV
electricity generation.
Table 5: Economic value of PV/T thermal energy
MVHR Product Options and Performance Assessment
Today, a large section of MVHR products are readily available on the market; thus, for
the further performance assessment, some typical systems were selected in view of the
Thermal energy generation using 14% crystalline silicon PV/Thermal system
with the roof tilt of 30
o
and air flow of 0.5m/s
Thermal energy generation = 3,440 kWh / year
Value of thermal energy (T) = 3,440kWh x £0.04 = £ 137.60 per year
(Retail price of mains gas @ £0.04/kWh)
Economic value of thermal energy generated (savings) =
£137.60 per year
