UK microgeneration. Part II: technology overviews

Abstract

This paper reviews the current status of microgeneration technologies at the domestic scale. Overviews are given for nine such technologies, grouped into three sections: (a) low carbon heating: condensing boilers, biomass boilers and room heaters, air source and ground source heat pumps; (b) renewables: solar photovoltaic panels, flat plate and evacuated tube solar thermal panels and micro-wind; and (c) combined heat and power: Stirling engines, internal combustion engines and fuel cells. Reviews of the construction, operation and performance are given for the leading commercial products of each technology. Wherever possible, data are presented from the field, giving the actual prices paid by customers, efficiencies and energy yields experienced in real-world use, reliability and durability, and the problems faced by users. This information has a UK focus but is generally relevant in the international context. Two issues are found to be prevalent throughout the microgeneration industry. Total installed costs are a premium and vary substantially between technologies, between specific products (e.g. different models of solar panel), and between individual installations. Performance in the field is found in many cases to differ widely from manufacturers’ quotes and laboratory studies, often owing to installation and operational problems. Despite this, microgeneration has demonstrated substantial improvements over conventional generation in terms of fossil fuel consumption, carbon dioxide emissions and energy cost, provided that the appropriate technologies are employed, being installed and operated correctly according to the load requirements of the house and their physical location.

Current status of fuel cell based combined heat and power systems for residential sector

“…SO 2 emissions are eliminated during FC-CHP operation because it is typically removed in an absorbed bed before reformate is processed. Table 5 summarises the industry-average levels of airborne pollutants like NO x , CO and particulates from fuel cells, condensing boilers and CHP engines [54,55]. Measured emissions of airborne pollutants from fuel cells are around a tenth of those from other gas-burning technologies, as shown in Table 5.…”

What role for microgeneration in a shift to a low carbon domestic energy sector in the UK?

“…Meanwhile, uncertainty surrounding grants pushes PV installers to focus on maximising sales (Keirstead 2007), and unrealistically low payback times advertised by some manufacturers are a dangerous sales tactic (Staffell et al 2010). The Welsh Consumer Council (Bibbings 2006) reports the reputation problem of the solar thermal industry, in which some have aggressive sales tactics and inflated prices.…”

The 20% house – An integrated assessment of options for reducing net carbon emissions from existing UK houses

“…Utilisable heat can be recovered from the engine's cooling jacket and an exhaust gas heat recovery unit. Micro CHP IC units typically have electrical efficiencies of 24-30% and heat to power ratios of 2.5-2.0 [18]. An IC engine generates electricity as soon as it is up to speed but takes some time to heat up to a temperature where useful heat can be extracted.…”

“…There is extensive literature on the application of micro generation to domestic properties including several integrated appraisal papers [5][6][7][8][17][18][19]. Most of the previous studies have concentrated on the carbon savings which are likely to result from the use of a particular micro generation technology.…”