Solar-thermal collectors and photovoltaic panels are effective
solutions for the decarbonisation of electricity and hot water
provision in dwellings. In this work, we provide the first insightful
comparison of these two competing solar-energy technologies for
the provision of combined heating and power (CHP) in domestic
applications. The first such system is based on an array of hybrid
PV-Thermal (PVT) modules, while the second is based on a solarthermal
collector array of the same area (based on a constrained
roof-space) that provides a thermal-energy input to an organic
Rankine cycle (ORC) engine for electricity generation. Simulation
results of the annual operation of these two systems are presented
in two geographical regions: Larnaca, Cyprus (as an example of a
hot, high-irradiance southern-European climate) and London, UK
(as an example of a cooler, lower-irradiance northern-European
climate). Both systems have a total collector array area of 15 m2
,
equivalent to the roof area of a single residence, with the solarORC
system being associated with a lower initial investment cost
(capex) that is expected to play a role in the economic comparison
between the two systems. The electrical and thermal outputs of the
two systems are found to be highly dependent on location. The
PVT system is found to provide an annual electricity output of
2090 kWhe yr-1
in the UK, which increases to 3620 kWhe yr-1
in
Cyprus. This is equivalent to annual averages of 240 and 410 We,
respectively, or between 60% and 110% of household demand.
The corresponding additional thermal (hot water) output also
increases, from 860 kWhth yr-1
in the UK, to 1870 kWhth yr-1
in
Cyprus. It is found that the solar-ORC system performance is
highly sensitive to the system configuration chosen; the particular
configuration studied here is found to be limited by the amount of
rejected thermal energy that can be reclaimed for water heating.
The maximum electrical output from the solar-ORC configuration
explored in this study is 450 kWhe yr-1
(50 We average, 14% of
demand) for the UK and 850 kWhe yr-1
(100 We average, 26% of
demand) for Cyprus, however, the study helps to identify aspects
that can lead to significant improvement relative to this estimate,
and which will be at the focus of future work. An economic
analysis is also undertaken to investigate the installed costs and
lifecycle costs of the two systems. Without financial incentives
both systems show long payback periods (14 years in Cyprus and
18 years in the UK for the PVT, and >20 years for the solar-ORC).