Urban energy generation: The added value of photovoltaics in social housing
Introduction
Urban energy generation at the small scale can be defined as micro-generation and is simply the generation of energy—heat or electricity—by individual buildings or small groups of buildings. The technology that provides this energy distinguishes itself from that traditionally used in that it gives occupiers the responsibility to produce energy to partly sustain their homes or buildings. Micro-generation technologies include photovoltaic (PV) installations, micro-combined heat and power systems, micro-wind, solar thermal systems, fuel cells and micro-hydro systems. There is a huge potential to utilise this type of technology in the urban built environment not only to satisfy demand and provide decentralised generation but also to help tackle fuel poverty and achieve reduction in emissions.
In the United Kingdom (UK), the Government has set short term targets of reducing the country's carbon dioxide emissions to 20% below 1990 levels by 2010, to achieve 10% of electricity generation from renewable sources and to install 10 GW of combined heat and power capacity by the same year. In response to these targets and the provisions in the Energy White Paper (and subsequently, the UK Energy Act 2004), there have been two primary initiatives aimed at encouraging the installation of microgeneration technology—Clear Skies2 (solar thermal), and the Major Photovoltaic Demonstration Programme with total funding over 4 years of around £42.5 m [1]. In essence, the emphasis of these programmes is that if buildings can be made energy efficient and produce their own energy this will not only have a real impact on overall energy demand but also in tackling climate change.
In addition to the known environmental benefits, the impact of urban renewable energy generation on the occupier of a building can provide another impetus to justify its use and added costs. If one considers PV, as an example, there are now many exemplar buildings in which this technology fulfils the role of multifunctional building component [2], [3], [4]. Specifically, the use of PV laminates to provide weather protection, solar gain/solar shading control and also generating electricity. This is a testament to the flexibility of PV as a micro-generation technology in the built environment.
PV technology can also be considered in terms of both its direct and indirect energy benefits [5]. The direct benefit is clearly one of sustainable electrical power generation and also in financial savings. Indirect benefits are more subtle and span ‘softer’ issues such as pride in housing and increased energy awareness to technical issues such as generation at point of use, grid strengthening and, as will be highlighted here, the potential for demand reduction. It can also be argued that the use of PV when combined with occupier perception and behaviour can result in further environmental benefits or additionality that has not been previously reported. The linkage of occupier perceptions, energy generation and utilisation through surveys and system monitoring, as will be discussed in this paper, can highlight social, environmental and economic benefits aspects that are worthy of consideration when studying energy in buildings—especially in social housing.
Section snippets
Social housing
The cost of housing in the UK is extremely high. This applies equally to both rented accommodation and homes for ownership. This cost creates major problems as many critical public sector staff such as teachers; nurses and police are not able to afford housing close to their place of work. In addition, a significant proportion of the population either on low salaries or on social benefits cannot compete or afford such expensive housing. As an example, the average price of a house in the South
Urban energy generation (micro-generation)
Micro-generation—small scale electrical power generation at point of use—is seen to offer a range of potential benefits to both the homeowner and the network operator. Small scale PV such as that used in buildings (BiPV) can be termed as a micro-generation technology. It can be combined with other electrical power generating technologies such as wind (micro-wind) and micro combine heat and power (micro CHP) to arrive at what can be termed as urban energy generation technologies. Micro CHP is
Tariffs and subsidies
In terms of economics, energy efficiency and sustainability of domestic microgeneration technologies in the UK, it is generally very important to avoid export of generated electricity (or heat) [5]. In general, the tariff that a homeowner is paid for export of electricity to the grid is a fraction of the import cost. Typically, in the UK for example, a homeowner would be offered payment at ∼£0.02/kWh for electricity export, compared to being charged ∼£0.07/kWh for import. This poor tariff may
Electricity generation and demand
In the future, the advent of variable domestic electricity price tariffs (price rises and falls with demand during the day, following the centralised generation tariff) will increase the benefit of avoided export and enhance the use of more pro-active energy management schemes within buildings or houses.
As can be seen from Eq. (1), the advantage of a generation tariff rather than an export one is that there is a financial benefit to the homeowner in trying to avoid export of electricity from
Energy analysis in a social housing scheme
The thrust of this work is based on a recent social housing development located on the western side of Leigh Park in Havant, Hampshire. Leigh Park, built in the 1950s, was, at the time, Europe's largest social housing overseen by a local authority, but with the ‘right to buy’ many of the properties are now privately owned. The site is bounded by a school to the north, residential properties to the west and south and industrial units to the east. Before being developed this site was a car park
Added value of PV in social housing
The PV generation, import, export and consumption profiles for house H4 over a 24 h period (07/08/2004) is shown in Fig. 8. Over 70% of the PV generated electricity is exported from the house during this day. This is despite the fact that, over the entire day, the overall demand is 69% higher than the 8.2 kWh (integrated area under the bell curve) of electricity generated by the PV system. If the base load demand is accounted for it is clear that there are virtually no ‘active loads’ between
Conclusions
The use of building integrated photovoltaics in social housing developments in the UK can provide a significant contribution towards the annual electrical demand and an overall reduction of the fuel burden. Active load matching can enhance the financial return to the homeowner but current tariff schemes penalise energy efficient users in comparison to their high-demand neighbours. It has been shown that for very peaky profile users, with prolonged periods of high electricity consumption in both
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