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
238
CO
2
emissions are less than zero and the negative quantity about the cost implies a
positive financial benefit to the house user.
Figure 19: SAP results for the benchmark option ZEMCH109
Assessment of Energy Demand, Carbon Emissions and Heat Loss
The delivered energy, CO
2
emission, primary energy and annual operating cost of 34
design options were conducted based on SAP 209 calculation method (Fig 20). The
results indicate that when a wood pellet system (OPT 32) is applied to the house, the
energy demand is estimated to be the highest among other options although the system
leads to zero carbon operation. This could be derived from the associated low CO
2
factor,
yet it has no contribution to the energy use itself. However, the use of a wood pellet
boiler system is considered to be costly in terms of its operating energy cost. In SAP
2009 calculation, the unit price of mains gas is estimated at 3.10p/kWh while that of
wood pellets is 4.93p/kWh. Similarly, when a combi-boiler is applied, the delivered
energy remains high although CO
2
emissions can drastically be reduced (OPT 23). The
installation of a ground source heat pump helps reduce total energy use due to the high
COP but it needs to be accompanied by properly sized additional renewable energy
technologies, e.g. PV, that can supply electricity for the operation (OPT 26). Also, this
tendency can be applied to the use of air source heat pump (OPT 1). There is no or
marginal difference in energy use between radiators, under-floor, and radiators + under-
floor space-heating alternatives (OPT 22-34). Moreover, the study found that using PV
along with the systems is beneficial (OPT 5-20, 22-24, 26, 27, 29, 31-33) as opposed to
situation where PV is not in use (Table 2).
-24.43
-52.06
-71.31
-2.8
-80
-70
-60
-50
-40
-30
-20
-10
0
Delivered energy (kWh/year)
CO2 Emission ( kg/year)
Primary Energy ( kWh/ year)
Annual Operating Cost ( £/year)
