Abstract
Performance calculations are presented for a small-scale combined solar heat and power (CSHP) system based on an Organic Rankine Cycle (ORC), in order to investigate the potential of this technology for the combined provision of heating and power for domestic use in the UK. The system consists of a solar collector array of total area equivalent to that available on the roof of a typical UK home, an ORC engine featuring a generalised positive-displacement expander and a water-cooled condenser, and a hot water storage cylinder. Preheated water from the condenser is sent to the domestic hot water cylinder, which can also receive an indirect heating contribution from the solar collector. Annual simulations of the system are performed. The electrical power output from concentrating parabolic-trough (PTC) and non-concentrating evacuated-tube (ETC) collectors of the same total array area are compared. A parametric analysis and a life-cycle cost analysis are also performed, and the annual performance of the system is evaluated according to the total electrical power output and cost per unit generating capacity. A best-case average electrical power output of 89W (total of 776kWh/year) plus a hot water provision capacity equivalent to ∼80% of the total demand are demonstrated, for a whole system capital cost of £2700–£3900. Tracking PTCs are found to be very similar in performance to non-tracking ETCs with an average power output of 89W (776kWh/year) vs. 80W (701kWh/year).
Highlights
This paper has presented a technoeconomic model to investigate the potential performance and cost of a domestic-scale combined solar heat and power (CSHP)-Organic Rankine Cycle (ORC) system featuring a positive-displacement expander, for use in the UK
The results of initial simulations based on simple component efficiency data, load profiles and operational control regimes have shown that the electrical output from the system is sensitive to the flow-rates, temperatures and working pressures in the ORC sub-system and to the design and operation of the solar collector array
Annual simulations have shown that for a fixed flow-rate system operation with 15 m2 [46] of rooftop collector array, the system can produce an average power in the region of 80–90 We (700–780 kW he/year) for an approximate total capital cost of £4400–5500, of which only £2700–£3900 can be attributed to electrical power generation and the rest to solar hot-water heating
Summary
Between a quarter and 30% of the total CO2 emissions in the United Kingdom are associated with domestic energy use [1,2]. International Energy Agency (IEA) published a roadmap [3] for emissions reduction over the four decades, detailing the expected contributions from a range of improvements and technological developments. In this roadmap it is predicted that end-use fuel and energy efficiency will provide the largest proportion of the emissions reduction, contributing 38% of the overall target, while renewables are expected to provide a further 17%. Together, these account for more than half of the overall target and are the areas in which the domestic sector can play a significant role. Cumulative PV demand exceeds 2.5 GW, with 93% of this demand having being realised in the past two years and 52% being attributed to the domestic sector [8]
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