Money for new energy07 June 2010

Building energy strategies are changing thanks to the latest government incentives. Dr Tom Shelley reports

The economic landscape for meeting building energy requirements is in the process of changing dramatically, following two main developments: the Feed-In Tariffs, for energy generated from renewable sources, which have already gone live; and the Renewable Heat Incentive, which is scheduled to be introduced in April 2011, if we can trust the promises of politicians.
At the same time, conventional HVAC equipment and energy management systems continue to become cleverer and more efficient. So it really is time to take a hard look at what plant engineers have or are proposing to buy, to see if we might do better.
The new government subsidies arise because, wisely or unwisely, the UK has agreed to a 15% renewable energy target by 2020, as part of the European Union's binding commitment to 20%. Since all energy from renewable sources in the UK totalled just over 2% in 2008, and heat generated from renewable sources was about 1%, appreciable financial incentives are seen as the route to encouraging use of renewables – partly buoyed by the hope and expectation that this might lead to the development of new UK-based exporting industries.
Feed-in tariffs (www.fitariffs.co.uk) give a payment for every kilowatt-hour of energy produced from renewables, plus an additional payment for surplus energy exported to the grid and a saving on energy purchased from electricity suppliers. Payments range from 9p/kWh for large scale anaerobic digestion (biogas) to 41.3p/kWh for small scale photovoltaic retrofits. Maximum size for subsidised installations is 5MW.
Meanwhile, the Renewable Heat Incentive is, at time of writing, still undergoing 'consultation' and, assuming it happens, will attract payments, yet to be decided, from next spring. For this subsidy, there is to be no limit on size. The inevitable red tape can either be handled by a system provider or users can struggle through the procedures themselves.
Most of the technologies available to take advantage of these schemes are, at the present time, foreign made. Mitsubishi Electric, for example, has launched a new range of heat pumps, using air, water and ground sources, with capacities from 25kW to 200kW. Heat pumps are expected to qualify as renewables, as they harvest free heat energy, producing 3.5kW to 5kW of heat for every 1kW of electricity they consume. The Mitsubishi products can each supply hot water at 70ºC, water for radiators and under floor heating at 45ºC or warm air for ducted heat systems.
Heat pumps were considered economically viable even before the new scheme, and have been used for years in Scandinavia. The only downside to air source heat pumps is that, in cold, damp weather, evaporator coils are liable to ice up, so reducing efficiency. Indeed, in worst case scenarios, because the efficiency of electric power generation and transmission from gas fuel is only around 35%, it can be argued that a modern gas-fired condensing boiler has about the same impact on the environment as an electrically-driven heat pump, although a new boiler will not attract a subsidy.
Potterton Commercial's new Eurocondense Three boiler is smaller and lighter than its predecessors, with a reduced footprint. Internally, it has a sectional aluminium-silicon alloy heat exchanger and a single burner assembly that slides out for servicing. Hydraulic, electrical and flue connections are all now top-mounted, saving floor space and making the boiler compatible with pipework header and flue kits.
Noise is also down to 54dBA at 1m, as a result of redesigning the fan, bearings and inner acoustics. The boilers are available with 125, 170, 215, 260 and 300kW outputs. Up to 15 boilers can be installed in line or back-to-back, producing a maximum combined output of 4,500kW. NOx is less than 35mg/kWh, which is half the requirement of the most stringent Class 5 category in EN 483:2000.
Moving on, for plant engineers interested in taking advantage of Feed-In Tariffs, there are a number of new foreign ideas now being marketed in the UK. One is the Heatcatcher, which uses waste heat to generate energy by a Rankine cycle – but not one that involves boiling water to make steam. It is manufactured by Calnetix Power Solutions in Florida, but marketed in the UK by Efficient Air in Polegate, East Sussex.
Managing director Darren Bryant says that the units capture heat using water, but harness refrigerant RT45FA as a working fluid, with a microturbine connected to an alternator running at 20,000 to 120,000 rpm to produce power. Typical cost for a 100kW unit is around £250,000 but, as he explains: "If they were to sell more, the cost would come down." Some are apparently already in service in Spain and Italy.
An alternative strategy to consider, taking advantage of the high feed in tariffs for photovoltaics, is adopting Evalon photovoltaic roofing membranes and Solyndra photovoltaic rods. These use the same basic PV material, rolled up into cylinders. Both are only suitable for flat or very gently sloping roofs, and both are being marketed by ICB (Solar) in Bournemouth.
Chris Rigney of ICB claims that the cost is about £6,000 to £6,500/kW peak and the panels are typically 10.5 to 12.5 metres square. (As a rough guide, average output over 24h is 20% of peak power). The PV films use copper indium gallium di-selenide CIGS, which makes them 12% to 14% efficient. That is much better than the alternative membrane PV material, amorphous silicon, at 4% to 5% efficiency, but not quite as good as crystalline silicon, which comes in at around 20%.
Evalon is a long established German roofing membrane, which can now be made additionally as PV film, merely requiring that the slope of the roof cover be at least 3º. Solyndra is the name of the Californian firm with the CIGS technology and the maker or the cylinders. The advantage of the cylinders is that they allow air to pass between them, so avoiding building overheats in hot weather, and they harvest energy both from direct sunlight and from light reflected from beneath.
Both systems have been installed on various industrial, commercial and public buildings in the UK, as well as in Continental Europe. Public buildings predominate, simply because public authorities have access to capital. Most commercial firms with limited capital resources have to set priorities – and the first, in many cases (and still the most cost-effective) measure is to improve thermal insulation.
BASF has been taking a miniature passive building on a semi-trailer around Europe, to demonstrate how to construct a building that requires almost no conventional heating or air conditioning, yet remains warm in winter and cool in summer. The 24 metre square building, called MESH (mobile energy saving house), is made from wood, but uses BASF's Neopor expandable polystyrene for facade insulation, with Styrodur extruded polystyrene rigid foam panels beneath the foundation slab, on the flat roof and around the perimeter.
Its solar thermal panels use Basotect open cell melamine thermoset resin foam insulation. In the triple glazed windows, two flat strips of Ultradur polybutylene terephthalate are extruded into the profile, replacing thermally conducting metal reinforcement, at the same time avoiding thermal bridges and reducing weight by 20%. And on the surface of the glazing, a foil coating made by German company Hornschurch includes three BASF pigments to reduce heat build up.
By the way, a passive building, as defined by Germany's Passivehausinstitut Darmstadt, has a residual heat demand of 15kWh or 1.5 litres of heating oil per square metre per year, for heating. The total quantity of primary energy used for any extra heat, hot water and electricity must not then exceed 120kWh/m2 per year.
Finally, while on the subject of heating and air conditioning, remember that very large savings, with short paybacks, can be achieved by using variable speed drives to control the speeds of ventilation fans and circulation pumps. Since fan and pump energy consumption tends to ramp up as the cube of speed, running one at, for example, half speed (as opposed to switching it on and off in equal time intervals at full speed) reduces energy consumption by a full 75%.
Since the price of power electronics has come down while the cost of energy has gone up, payback times are very often down to eight months or, at most, two years. Add in the fact that fan noise tends to go up according to the speed raised to the fifth power, and using drives wins all round.
Latest examples of cost savings include £29,000 on the annual electricity bill for the Jackson House office block in Manchester and £6,000 annual savings for the Castlegate Business Park in Monmouthshire. Jackson House has four ventilation fans, driven by motors rated at 45kW to 120kW, plus four pumps for the heating system. Payback time was 11 months.
Castlegate Business Centre has two fans, rated at 22kW and 15kW. In its case, payback time was 16 months. Both projects used drives from ABB.

Tom Shelley

Related Downloads
25545\Money_for_new_energy.pdf

This material is protected by MA Business copyright
See Terms and Conditions.
One-off usage is permitted but bulk copying is not.
For multiple copies contact the sales team.