Get Sust! issue 43

FEATURE

The power factor: which way is the wind blowing?

Sustainability in buildings is fundamentally about the efficient use of energy (and other natural resources). Conventional energy generation and distribution are complex, specialised and highly politicised topics, so Get Sust rarely ventures into that neck of the woods. But when the keynote speaker at last month’s CIBSE Conference (28–29 April) is Professor Julia King, a government advisor on mitigating climate change, and she’s swiftly followed to the platform by the general manager of Shell Gas Direct, it seems that generating power is currently a hotter topic than cutting its usage. Get Sust sat in on Day 1 of the Conference, and went home wondering which way the wind was going to blow next…

Professor King, currently Vice-Chancellor at Aston University, addressed the CIBSE delegates in her role as a member of the independent Committee on Climate Change, whose inaugural report ‘Building a low-carbon economy’ was part of the driving force behind Chancellor Alistair Darling’s announcement (on 22 April 2009) of the UK’s first legally binding carbon budget.

In a fast-moving presentation, crammed with raw data (see link below), Prof. King explained the reasoning behind the shift from the UK’s original intentions of a 60% cut in carbon emissions by 2050, to the new long term goal of 80%. It’s no great mystery really – the CCC’s analysis of the scientific data suggests that, globally, we’re just not delivering the reductions in emissions we need if we are to avoid dangerous rises in temperature.

What is different is how we might set about achieving the targets. Whereas in previous years speakers at CIBSE Conference have understandably banged the drum for ever-increasing efficiency and reliance on renewables, now the rhythm is hotting up (as is the climate) and renewable energy technologies suffered quite a bashing (see below). Carbon capture is, it seems, now viewed by government as the quickest and most efficient way out of the jolly fine mess we’ve got ourselves into – with a dollop of nuclear and a dash of renewables thrown in for good measure.

The logic of Prof. King’s argument is uncomfortable, but clear. Exhortations to save energy are not delivering the goods fast enough, even with incentives. Consumers find it hard to make informed decisions about their energy-using habits (e.g. if you switch off your TV or PC at night, is it OK to carry on buying green beans flown in from Kenya?). And, in a market-led economy, how can you expect power generation companies to invest in measures that mean there will be a drop in demand?

Thus the simplest way to reduce carbon is to tackle it right at the start of the process, so that businesses and consumers don’t need to worry. In order to do this, though, it will be necessary to use electricity to deliver heat, and to find technical fixes to reduce indirect losses.

This isn’t to say that energy efficiency and renewables don’t have a role to play. With the cost of power inevitably rising, efficiency is crucial; and buildings-related renewables such as solar water heating and photovoltaics can provide an alternative low-carbon option – it’s just that they don’t suit every building.

Mike Hogg of Shell Gas Direct presented his organisation’s take on the situation in the form of two ‘scenarios’ – the ‘scramble’ and the ‘blueprint’. Underpinning these alternative versions of the future is his assessment of the present: global demand is growing; new sources of gas and oil can only serve to keep up with depletion of existing sources; coal has infrastructure problems; biofuels take up valuable land; nuclear power has political and environmental baggage; and renewables have barely got off the starting blocks in terms of capacity.

So you won’t be surprised to hear that the ‘blueprint’ for a way forward, according to Shell Gas Direct, is for coalitions between key companies and countries, thinking about the demand side, and carbon-driven pricing systems. Choice of fuel will be based on which emits the least carbon.

Further evidence of the strength behind the carbon capture approach was presented later in the day by Matthew Rhodes (on the truth about wind power) and James Thonger of Arup, who explained that tri-generation has not yet lived up to expectations, mainly because the original expectations were too high!

Hot air?

Matthew Rhodes of Encraft has conducted a comprehensive study of wind power in the UK. Presenting his findings to conference, he said there are two truths about wind power:

* it is not a single technology

* performance depends on location, design and the skill of installation.

He has studied the performance of 29 turbines across the UK, mostly in urban locations, ranging from large commercial installations to community turbines. His headline result is that the payback for a micro-turbine (the kind people attach to their homes) could range from 40–500 years! This is because it is virtually impossible to predict performance, but also because many systems have been either badly installed, or the wrong type of device was chosen.

Some of the machines he looked at could have performed 30 time better if they had been located elsewhere (e.g. on the coast). He found that the UK national windspeed database (known as NOABL) sometimes overestimated windspeeds by 40%, leading to performance predictions being out by a factor of 8.

He was careful to underline that he doesn’t lay the blame for this at any particular door, and to stress that the situation has already improved, not least because real wind data is now easier to come by. But the difficulties encountered by early adopters could harm the uptake of wind technology in the future. In conclusion, he said that the psychology of wind is good (a visible sign of thinking green), but the rush to get in on the act did more harm than good.

Similar conclusions could be drawn from James Thonger’s presentation ‘Trigeneration: can it ever live up the the hype?’

Trigeneration, which delivers electrical power plus useful heat and cooling, has found favour in high places – chiefly at the Greater London Authority, which adopted it as a policy requirement. But when Dr Thonger delved into the calculations underpinning this decision, he found that they were awash with errors and misplaced assumptions, particularly in terms of the amount of primary energy that can be ‘saved’ (i.e. not used in the first place).

Overall, he found that CHP driven by natural gas makes a primary energy saving of 18%, but if the system is linked to a heat network only 9% of primary energy is saved (because of the need to power the pumps and other plant). Even micro-CHP schemes do not really displace primary energy. He describes this as like ‘buying a gas-guzzling Jeep instead of a Lamborghini’; in other words, you are choosing an inefficient system instead of a very inefficient system!

Presenting a case study of the Natural History Museum, where the CHP system began in January 2007 (with cooling added to the mix in June 2007), Dr Thonger calculated that the overall coefficient of performance was 0.61, and that the total primary energy saving was -10.4% (and worse, -19.6% in 2008).

His conclusion: ‘If a co-generation installation is less efficient than conventional supply (using the same fuel source), it cannot claim to save carbon. It’s that simple.’

Engineering a DEC

Elsewhere on the CIBSE conference programme there was further evidence of dissenting voices and heart-felt rethinking of ‘green’ strategies. David Fisk, Professor of Engineering for Sustainable Development at Imperial College London wants us all to go back to good old-fashioned calculations and ditch eco-jargon such as ‘sustainable’, ‘iconic’, ‘eco-anything’ and ‘renewable heat’ (quipping that architects think this means you can use it again!). His entertaining presentation had a serious side, though. He suggests a new three-point approach to approach to design: ‘engineering a DEC’

1. Begin the design process with a specific outcome in mind – achieving a display energy certificate (DEC) rating of B, say. Aim high, in the knowledge that buildings tend to drop a level or two below expectations.

2. Introduce ‘ship trials’ – test the building; get the commissioning right (this can take a year or more).

3. Make the most of design technology – use data from computer-aided engineering to ensure that the building works as intended, and let the clients use the data to help them carry on doing so.

Wyatt’s windows

Another voice calling for a rethink was Terry Wyatt of Hoare Lee who, to the amusement of the CIBSE audience, recalled his school days as a ‘window monitor’, and spoke out in favour of displacement ventilation in classrooms – a topic that also raised some passion at the end of the day in a debate on school design.

It wasn’t all so hard hitting. There was a good mix of case studies on sustainable supermarkets, infrastructure for aging universities, water efficiency studies, and reports of new developments in pumps and chillers.

But after a decade or more of fast-moving and exciting new techniques and technologies, it was refreshing to take a ‘reality check’ and reassess what really does work. Not sure what OFSTED would say about the window monitors, though!

Learn more:

	•	Presentations from all the speakers during the two-day conference can be viewed at www.cibse.org/conference2009.
	•	The CCC’s inaugural report ‘Building a low-carbon economy — the UK’s contribution to tackling climate change’ was published on 1 December 2008. The report contains the CCC’s recommendations on the 2050 emissions reduction target and advises on the levels of the UK’s first three legally binding carbon budgets for 2008–2022. Visit www.theccc.org.uk.
	•	NOABL is managed by BERR www.berr.gov.uk/energy . For more on wind power, contact the British Wind Energy Association, BWEA, the trade and professional body for the wind energy industry. See in particular www.bwea.com/noabl.
	•	Matthew Rhodes (www.encraft.co.uk) has published his results at www.warwickwindtrials.org.uk.
	•	James Thonger’s data is available at www.cibse.org/conference2009.

© Melanie Thompson 2009