Combined heat and power will change the way many of us think about energy in our homes. We find out what contractors must do to benefit from the rise and rise of domestic chp.
Last month, Powergen started selling domestic combined heat and power (dchp) units in the UK. It's the first time consumers have been able to get their hands on the technology without taking part in a technical trial.

CHP – the simultaneous generation of electricity and heat – brings to mind large commercial, industrial or district heating schemes. Today, similar technology is available for the home, replacing the gas-fired boiler with a device that supplies both hot water and electricity (see figure 1, below). If a household generates more electricity than it needs, it sells the excess to the local electricity company.

DCHP units cost more than a boiler, but homeowners can expect to shave between £100 and £200 from their energy bills every year.

Opportunity knocks
The potential market for dchp in the UK is vast. According to a report prepared for the Energy Saving Trust last year by Tim Crozier-Cole and Gareth Jones, 17 million households in Great Britain have gas-fired central heating – and each year 1·3 million of them replace their boilers.

David Moriarty is managing director of Whisper Tech, the New Zealand company that is supplying 400 of its WhisperGen units to Powergen to sell in the UK. He reckons that his company and others could sell up to 700 000 dchp units in the UK every year.

Taking advantage of this £1·5 billion-a-year market will be tough, however. Legislators are busy trying to remove institutional barriers (see 'The regulatory background', over), but there is a more pressing practical problem – who will install and service the equipment? In their report, Crozier-Cole and Jones say that dchp installers need electrical, gas, central heating, plumbing, building and manual handling skills. Also, commissioning demands "competency to check the electrical interface and notification to the distribution network operator".

"Finding people to perform these tasks for micro-chp will be difficult," they say, "and installer training will be a key factor in successful deployment."

One solution, at least in the short term, would be for manufacturers of dchp equipment, or utilities that are selling it, to train their own installers. Utilities that supply both gas and electricity would benefit from sales of both fuels, and from the installation and maintenance of the hardware. During recent trials of Whisper Tech dchp units in Ipswich, Powergen arranged training for installers from local heating and plumbing firm JT Wilding.

Moriarty from Whisper Tech says: "We've installed 50 units in the UK over three years. Initially, we worked with EA Technology, which was employed as project manager of the trials. In the third winter, we were keen to see someone come in cold." Moriarty spoke to staff at JT Wilding, who were initially sceptical. "Having had about one day's training and completed 15 or 16 installations, they are now one of our biggest advocates."

But are there opportunities for electrical contractors? Phil Buckle, business development director at the National Inspection Council for Electrical Installation Contracting (NICEIC), recently visited JT Wilding and one of the trial dchp installations in Ipswich. He was impressed by what he saw.

"I think electrical companies need to look at this as an opportunity," he says. "There clearly is a gas element that has to be done by a Corgi-registered fitter, but that's not to say an electrician can't become Corgi-registered. There is a connection to the mains supply, and that should be done by someone who has electrical competence."

Moriarty says installation will appeal to larger, multidisciplinary firms that combine electrical and mechanical skills: "We see it as a job for a gas fitter or plumber in larger firms who have a sparkie, or who work with an electrician. There is a role for the electrician in conjunction with a gas fitter, but it is principally a gas fitter's job."

A significant electrical element in any dchp installation is replacement of the electricity meter. The distribution network operator must measure the amount of electricity the household takes from the public supply and the amount the dchp installation exports, but most electricity meters only operate in one direction to prevent fraud.

George Francis, a senior electrical engineer at Advantica – formerly British Gas Research & Technology – says: "At present, only meter operators or their representatives can change a meter, so that will probably have to be done before installing domestic chp."

Service game
In the longer term, the equipment will need servicing. "Customers expect domestic chp to be as reliable as a boiler or an internal combustion engine," says Moriarty. The WhisperGen units are designed to operate for 3500 hours a year before servicing. "There's an annual service requirement, very similar to servicing a boiler," says Moriarty. The Stirling engine at the heart of the WhisperGen is sealed for life, and the control electronics cannot be serviced. So servicing consists of checking the boiler, the gas valve and the heat exchanger – a procedure almost identical to conventional boiler maintenance.

With plumbers handling the lion's share of the installation and maintenance, and the network operators changing the meter, does dchp offer any opportunities for the electrician?

"From our point of view," says Buckle, "we think we should encourage NICEIC Approved Contractors to offer their services." To this end, Buckle has suggested to Powergen that it could, during the current "market test" of dchp, work with NICEIC contractors.

The key to winning dchp installation work, say Crozier-Cole and Jones, will be reducing the number of people involved, ideally to one. But, as Buckle says: "Mechanical and electrical companies tend to keep the two disciplines separate." That will have to change if contractors are to take advantage of the "golden opportunity" that dchp represents.

The technical background

A domestic boiler converts about 70% of the energy in natural gas to heat. A condensing model might approach 90% efficiency. On the electrical side, things are much worse. Most large power stations are only around 50% efficient, and about 10% of the electricity they generate is lost in heating up the countryside on its way to your home.

DCHP tackles both of these problems by rivalling a condensing boiler’s efficiency and eliminating transmission losses. DCHP is also an inherently cleaner form of generation than most power stations.

Many technologies will generate heat and electricity at the same time, on a small scale. They include microturbines; internal combustion engines; Stirling engines; and fuel cells, which convert fuel directly into electricity.

The front-runner, at least in the short term, is the Stirling engine. It is an external combustion engine invented in 1816 by the Reverend Robert Stirling.

Unlike an internal combustion engine, in which the fuel mixed with air burns inside the cylinder, a Stirling engine works by alternately heating and cooling a sealed cylinder from the outside to produce useful work. Stirling engines are inherently reliable and efficient.

In the longer term, fuel cell-based dchp will probably take over. They promise to further improve efficiency and reliability, while cutting noise and vibration.

The regulatory background

The success of dchp will depend not only on trained installers and reliable technology, but on the rules and regulations that govern the UK’s electricity supply industry.

DCHP is bad news for distribution network operators that earn their money from “use of the system”, and they have no financial incentive to connect dchp generation to their networks. If it is to succeed, the fledgling industry needs connection agreements with network operators simplified and new metering and trading rules.

In October 2002, the Electricity Association published Engineering Recommendation G83, which covers generators producing up to 16A per phase in parallel with the distribution network. Under the earlier G59, which applied to generators of all sizes, the network operator could inspect and test all installations, adding to the cost. “G83 has been a liberator,” says George Francis from Advantica, “it encourages the installer as opposed to presenting barriers.” Under G83, the installer can fit equipment and inform the operator within 30 days. G83 also specifies the isolation, protection, earthing and electromagnetic compatibility requirements for micro installations.

The output of the large generators is matched to the consumption of customers in half-hourly periods. Obviously, it would be impractical to measure demand every 30 minutes, so the markets use “profiles” to estimate usage. This would be undermined if large numbers of small generators reduced demand.

There is a proposal, P81, to modify the UK’s Balancing and Settlement Code to remove the need for half-hourly metering of “third party generators at domestic premises”. Also, the New Metering Technology Working Group is developing a code of practice that will specify the way import and export energy should be measured. According to Dr Howard Porter of Beama Energy, it may also suggest a metering arrangement to measure gross generation (see figure 2).

Source

Electrical and Mechanical Contractor