|
In an increasingly uncertain world, the security of a country's power supply starts with energy efficiency and one of the most promising pieces of technology in terms of saving energy and protecting precious environmental resources is microCHP (micro Combined Heat and Power).
MicroCHP is an extension of the firmly established and well-proven idea of cogeneration (the use of a heat engine or power station to simultaneously generate both electricity and useful heat) to households or small office buildings.
A microCHP unit simply replaces the gas central heating boiler and provides heat and hot water as usual, but also provides most of the home's electricity needs. This locally generated electricity makes perfect economic and environmental sense when you consider the huge transmission losses that result from moving electricity from power stations to homes. And, by combining electricity generation with heating and hot water provision, even bigger energy savings and emissions reductions can be made.
Installation
A microCHP boiler is connected and installed in the precisely same way as a standard high-performance wall-mounted boiler and operates in the same way; the connections are identical and the electricity is even supplied to the domestic electrical installation via conventional electric plugs.
The boiler is controlled using a room thermostat and provides high efficiency heating and domestic hot water. Typically, it employs a Stirling engine. By allowing a gas in the engine to expand due to heat and then contract due to cooling, a piston is moved up and down in a magnetic field. This produces a current in the electrical coil around the cylinder with which alternating current is generated.
The Stirling engine ensures that a usable amount of electricity is generated as soon as the unit starts running to provide heat. Our own Remeha microCHP maintenance-free engine, for example, can generate 1kW of electricity, enough to meet a typical household's base electrical load. This electricity can be distributed in the home through the normal wiring.
By using a microCHP boiler, an average household can therefore generate a significant amount of its own electricity consumption annually. This results in a dramatic reduction in energy costs by as much as a quarter compared with condensing boilers, and even greater against standard efficiency boilers.
When the household's / small office's consumption of electricity is lower, any extra electricity generated is supplied to the grid through the meter cupboard, maintaining its electrical efficiency. The energy companies and the Government are currently working on a feed-in tariff for the electricity that is returned.
Strengthen the case
The microCHP boiler is a low to zero carbon technology (LZC), producing less than half the carbon dioxide emissions per unit of electricity generated than if the same amount of electricity were generated by a large power station. Planning regulations increasingly require the use of LZC sources to reduce CO2 emissions, strengthening the case still further for a microCHP based solution.
However, the benefits don't stop there. Payback on the boilers is particularly impressive for individual consumers who effectively get electricity for the price of gas. This can mean a 20-25% reduction in the total energy bill, equating to between €300 and €400 a year for an average household when compared to a condensing boiler. Savings will be even greater if replacing an old standard atmospheric boiler.
For society as a whole, the savings are on primary energy and CO2 at the power plant including a saving of 60% CO2 on the produced power. Although microCHP is no universal answer to the problem of climate change, it does have a significant, and, I believe, growing role to play as part of a mix of future heat and power producing solutions.
Financing microCHP
Our discussions with electricity supply companies have led us to be encouraged that microCHP could work economically.
For many of these companies, meeting their carbon targets is essentially all about financing rather than the technology itself.
They have the scale to be able to approach a large financial institution and borrow money to invest in microgeneration for their customers and then use the return tariffs to pay back the investment costs. This means the idea is effectively self-financing.
It is also a way for power generators to meet their carbon reduction commitments without transferring the cost of this to the customer. It also has the capacity to reduce fuel poverty because customers eventually have the microCHP boilers handed over to them once they have paid back the power generators investment costs.
The electricity generated may place a payback tariff on the customer for, say, five years but, in the meantime, the customers will be saving on their fuel bills because they are generating electricity and saving on gas through the microCHP boiler and, if they are replacing a condensing boiler, they get a significant payback so it is a win-win.
The state of microCHP in the UK
Combined heat and power (CHP) has come a long way since Thomas Edison's 1882 Pearl Street Station, a CHP plant producing electricity and thermal energy and using waste heat to warm neighbouring buildings.
Remeha is at the forefront of microCHP development and is currently field testing 100 microCHP units in the Netherlands with a further four in the UK. Results after one year are encouraging, with end users experiencing the same comfort level as they would with a normal condensing boiler.
For electricity production, the aim of the field trial was to generate 2,250kWh; the actual amount produced was 2,103kWh. For the electricity-heat ratio, Remeha was looking to achieve 16.3%; the actual figure was an impressive 18.9%. The company was hoping for an annual energy bill saving of €300 and actually achieved a reduction of €311. And, with this boiler, the decrease in CO2 emissions per household was 746kg. All savings made are when replacing a condensing boiler with a micro-CHP.
Based on these results, Remeha is developing a domestic microCHP unit with the same or better performances for commercial release.
