About us.....

Abingdon Carbon Cutters is a Community Action Group formed to help reduce the carbon footprint of Abingdon in response to climate change, and to promote a sustainable and resilient lifestyle for our town as fossil fuel stocks decline. We meet on the third Wednesday of each month at St Ethelwold's House, which is here.

At some meetings, we have guest speakers to present various topics, and at others we discuss our own personal actions to address climate change. The group has a focus on encouragement, both of one another, and of the town community.

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Friday, February 20, 2009

Meeting Notes from 18.02.2009

The room in St Ethelwold's house that is used for Carbon Cutters was full to more than capacity for the talk about using Solar energy by Chris Jardine of the Oxford University Environmental Change institute.

Chris' group at the University focusses on small scale renewables, and Chris' main focus is the use of small scale photovoltaic solar systems.

Chris started his presentation with a background of Climate Change and its' implications. He moved on to cover the proportion of UK energy (electricity) that comes from each of the major sources, and the proportion of domestic energy that is used in each of several categories.

It was made clear that insulation and efficiency activities are an absolute must before embarking on any solar energy project.

In the UK, each square metre received around 1000kWh of solar energy each year. To put this in perspective, an "average" household uses something in the region of 4000kWh of energy per year. Chris showed a slide highlighting the drop off in incident energy for roofs that are not directly south facing. The drop off was less than many people had anticipated. In order to check the solar energy received by the roof of your building, you can check online here.

Chris explained that a "solar cell" for heating water is a combination of 2 basic principles of physics: 1: Black materials absorb heat. 2: Glass produces a greenhouse effect, trapping heat.

He described a typical domestic solar hot water system, and that 4square metres of solar collectors combined with a 200litre hot water tank can provide around 50% of the annual requirment of a family of 4's hot water needs (estimated 150 litres/day). Such a system would save 1.5tonnes of carbon dioxide emissions if it replaces electric heating, and 0.5tonnes if it replaces gas.

The type of tank required for a solar hot water system differs from a standard tank, in that there are 2 heating coils: one to add solar-energy to the water in the tank, and one to allow the boiler to add heat.

Chris described the 2 technologies of solar collectors for hot water systems, both the flat-plate type and the evacuated tube type. He reminded the group that planning consent is not usually required for a solar installation, unless the building is a listed building, or inside a conservation area.

A typical domestic system could well cost in the range £2k - £10k: a £400 grant is available through the Low Carbon Building Programme. This is increased to 50% for community, educational and charity buildings.

Such a system might provide cost-pacyback within 10-30 years - the quickest payback coming if the property currently has electrically heated hot water. The side benefits in terms of improved efficiency ratings under the new HIP scheme were also noted.

There proceeded some time for discussion, and through the questions that arose, Chris made some efforts to describe the pitfalls through a badly configured system. The input of heat energy from solar collectors is much more efficient when the contents of the hot water tank is cold. On this basis, an optimally configured system will provide any additional "top-up" heat required in to the hot water tank from a traditional boiler in the evening. The energy savings from a solar thermal system can be reduced by up to three quarters, if the boiler top-up is wrongly timed.

Typical combination boiler systems are not compatible with solar thermal systems. However, it was reported that there are 2 combi-boilers available which can accept preheated water in.

The second half of the evening was spent on the topic of solar photovoltaics (electrical solar cells). A no-maintenance system, it was commented that the only other household goods with a 25 year guarantee are cast iron saucepans!

There are three types of photovoltaic solar cells, Amorphous, Monocrystalline, and Polycrystalline. Chris spent a brief moment explaining the differences, both in cost of manufacture, and in operating efficiency. The Polycrystalline "middle-ground" is the most common cell design used in domestic installations.

In order to make some sens of the numberst that are discussed with regards solar PV systems, Chris explained that the value declared as "kW peak" for a system is the maximum electrical output in full direct sunlight. A system rated as 1kW would be expected to produce around 750kWh in a year. This compares with around 3000kWh/year as the average household energy consumption for "lighting and appliances"

Chris showed a number of photographs clarifying the installation procedure for pitched roof-mounted PV solar cells, and spoke briefly about some of the novel architectural possibilities that exist around the integration of a solar PV system in to a building.

The discussion then turned to financial and economic matters. There does exist (with the right tariffs) the opporunity to gain an income from the generation of solar electricity. SSE currently pay 18p for every unit of "green" electricity that is provided to them. This value has increased 9-fold in the last 5 years, and could well increase further with the proposed introduction of a more formalised "feed in tariff system" in 2010. Germany has such a system, which currently pays the equivalent of 30p per unit for domestically generated "green" electricity. The GoodEnergy supplier will pay 10p for every unit of solar energy that is generated, regardless of whether it is used at the point of generation, or exported to the grid.

The cost of the components and installation of systems was discussed, and Chris left the group with a challenging question: How come we need the calculations proven to the n't degree to confirm payback time of a system like this, but we spend money on cars, holidays and toys without the same level of analysis. Chris would like to see people moving away from installing solar energy systems for "sound financial reasons" and to be more directly motivated by "doing the right thing".

There was more said and more discussed than the brief notes here. The links below are sources of further information.

Solar Trade Association – lists accredited installers

Vale Energy Team – general information and links about energy saving

Energy Saving Trust

Low Carbon Buildings Programme – gives Micro-generation Certification Scheme recognised installers and information about grant applications and conditions

Directgov site

Blewbury Energy Initiative

Reasonably Local Installers

Ardenham Energy Ltd
01296 331362

Heelas Heating and Renewables
01865 739788 / 0844 8001682

JHS Power Solutions
01295 786262

JOJU Ltd – PV only
0207 275 0176

Oxford Solar Ltd
07740 929305 / 0845 217 8970

Race Energy
01296 771045 / 0800 298 9336

01932 784848

Solar Solutions Direct
01865 884261

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