October 24th 2011

"Renewable Energy Solutions for the 21st century; technologies and the role they play in meeting targets."

         Damian Baker
Founder and MD of RenEnergy.

This talk drew a large and appreciative audience, since it focussed on one of the major concerns facing the world today. It also illustrated the role of the entrepeneur in today’s economy since Damian had created his business as a result of a personal requirement - underfloor heating in a barn conversion he undertook - for which he could not find a satisfactory solution. This led him in 2006 to form the company RenEnergy of which he is Managing Director and which has offices in Norwich, Hampshire and more recntly Yorkshire with a current employment of around 60 people.

In a holistic approach to renewable energy, Damian visited various European centres gaining background knowledge of the different systems and technologies used elsewhere for the supply of heating and energy to housing, with the clear advantages to a consumer of saving money but also in the long term of the desirable move to ‘green’ and renewable energy supply.

The Government currently adopts a ‘carrot and stick’ approach regarding renewable energy, the former through so-called ‘feed in tariffs and grants’ (essentially rewarding the consumer for using renewable energy sources) and the latter through strict regulations and calculation of overall carbon usage.

Familiar technologies already in use are wood-fired boilers and double glazing but it is important in evaluating advantages of such measures to include the real overall costs, such as transport of wood to areas devoid of a ready supply, or the energy required for manufacture of glass and, for example in the building industry, of cement manufacture.

In considering aspects of energy requirements and their provision, it is important to balance energy efficiency against renewable energy sources, and here insulation of property is a major concern. In ‘new build’ properties, it is easier to incorporate effective insulation (leading to low U values for walls) and it is also easier to fit solar thermal and solar photo-voltaic roof panels as well as ground source heat pumps and underfloor heating. In general, it is important to realise that, for maximum efficiency, lower flow temperatures are desirable in renewable energy systems, than in oil/gas fired boiler systems which typically might circulate water at 60-75 °C. Further, for older properties, the most satisfactory solution may well be a boiler using biomass as fuel, since a less drastic modification of the existing circulatory system will be required.

Photo-voltaic panels are the easiest technology for fitting and can offer the best return. There are three types of panels based on silicon: (a) monocrystalline (b) polycrystalline (c) thin film amorphous, with the first being the most expensive but also the most efficient. The range of efficiency values over the various types of panels could be in the region of 17% for (a) to 9% for (c). Currently, there are only two manufacturers of panels in the UK and most are manufactured in the far-east (e.g. China, South Korea). Germany, a country well-advanced in the use of photo-voltaics, has moved towards the use of thin film panels, having earlier largely used crystalline panels.

In the UK mixed forms are now often used which have an advantage in dull light conditions. As regards roof area required, 10-25 square metres is a typical value in the UK and, clearly, south (or near south) facing, non-shaded roofs are the most desirable.

Since the panels produce direct current (DC) a converter is required for conversion into alternating current (AC). These are very efficient (~95%). Through a switchboard, house usage is separated and is free whereas the excess electricity is fed to the grid. The ‘feed in tariffs’, whereby the producer is paid for generating the electricity and is also paid a rate for that electricity which is exported to the grid, are somewhat complex and are liable to change as Government policy changes but currently (2011) the tariffs are attractive since they are guaranteed for a given length of time. However, a review of tariffs is forecast in April 2012.

The current (2011) capital cost of an installation for an average house is £10,000-12,000 with a projected pay back time of 7-8 years representing an interest of around 9-12%. Suggested figures are for an annual income of ~£1000 and a carbon saving of 1-2 tonnes. The projected life of a panel is 25 years and at the present time there is a tremendous take-up of photo-voltaic generation, since the system is quickly installed and there is a good return on the investment. Usually, planning permission is not required except for listed properties or in a conservation area.

A nice example is the installation to a thatched cottage - clearly the roof offered no base for support of the cells but the householder was able to install the panels in an adjacent field which he owned! On new-build properties there is currently no VAT payable and it is just 5% otherwise. Improved encapsulation of the silicon panels means there should be no problems through exposure to the elements. An impressive example was shown of a 100 kW installation involving 504 panels. Special challenges can arise in fixing panels to non-standard roofing such as asbestos-fibre cement and from the weight of the installation.

The current popularity of photo-voltaic systems because of the generous feed in tariffs has led to some firms offering to install panels essentially for nothing, allowing the householder free electricity so-generated, but with the firm taking all of the feed in tariffs.

Energy conservation through the solar thermal route, whereby panels with circulating water in tubes are fitted to the roofs of properties, is best suited for provision of domestic hot water, which demands ~25% of household energy requirements with the rest being for space-heating. Solar thermal heating could provide up to 60% of the energy required for this domestic hot water. Although relatively straight forward to fit, the payback time could be ~30 years, although with proposed new incentives this could be reduced to ~12 years; the carbon saving would b about 380 kg per year. On very sunny days, considerably high temperatures can be achieved. More advanced technology uses evacuated tubes, which are sensitive to severe shock, and are suitable for large installations such as hospitals and hotels.

The technology behind ground source heat pumps can readily be understood in terms of the household refrigerator, whereby heat is taken from one source (in this case the inside of the fridge) and delivered into the room space (in this case the radiator-like pipework on the back of the fridge which gets warm when the apparatus is working). In the heating application, the heat source is usually through piping buried in the ground outside the property (over a large area - 1.5 to 2 times the floor area of the house - or buried as a long loop in bore holes). Alternatively, the heat source can be a water stream (very efficient) or through air flow (much less efficient) and the type of soil in ground-based applications is important since clay is good for heat transfer but sand is less good. The technology is reliable, easy to fit in new-build properties but not so easy as a retro-fit.

The current cost is ~£1500/kW. Such heat pumps are at a disadvantage in saving carbon because an electric supply is required for circulation of the fluid but they can be configured to use off-peak electricity and a carbon reduction of 60-70% can be achieved compared to heating with gas or oil. Pay back time is typically 10-12 years but in future this may be reduced through renewable heat incentives (provided the house is not heated by gas from the grid).

Biomass is an attractive proposition for heating provided there is a reliable supply chain for the wood-based fuel which, in the form of pellets, can be automatically fed using an Archimedian type screw feed. It is now the sysyem of choice for retrofit installations since such boilers can often be used as a direct replacement with little modification to internal plumbing.

The quality of the feedstock is important - the residue remaining after burning depends on this. An important consideration is the storage space required for the fuel which is relatively large. Since wood is regenerated in the biosphere, in terms of the fuel content biomass energy production is carbon neutral.

Damian concluded his survey on renewable energy by discussing how to buy a system appropriate for a person’s particular circumstance and finished with some pictures and data on a very modern private timber-framed house in Norfolk in which heating costs had been reduced to a very low figure using the available technology.

Alan Haines           26 October 2011