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Renew your energy: May 2012 Archives

Green Heat 3

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Community-based energy technology was very much a 1970s thing, but is now back on the agenda. An ESRC backed 'Sustainability Transitions' seminar series included a one day conference in Manchester in April which explored the 'lessons of the 1970s' for the current low-carbon transition. Organised by SURF (Salford Universities Centre for Urban and Regional Futures) and SPRU (Sussex Universities Science Policy Research Unit), the conference included a look- back at some of the pioneering work of the Centre for Alternative Technology, like. the 1976 Wates super-insulated house. Now PassivHaus projects are spreading everywhere.

CAT also pioneered inter-seasonal solar heat stores, with, in 1976, a 100 sq. m solar array feeding into a 100 cu. m heat store tank; see right. Others followed, like the 1980 Swedish 10,000 cu. m heat store - linked to 55 houses. See

Now there are many, and some are quite surprising.. For example solar heating might seem an odd choice for Canada, but the Drake Landing scheme in Alberta, with 52 houses, has 2,300 sq m of solar mounted on garages and an underground Inter-seasonal heat store:144 x 35m deep boreholes spaced 2.2m apart. There are many other interseasonal heat store systems around the world, the largest so far being the 13.5 MW Marstal project in Denmark.

In terms of efficient community-scale green heating, solar district heating backed up by interseasonal heat stores is arguably at the top end of the range in environmental terms, with almost zero emissions, but it's still expensive. District heating fed from other currently cheaper sources (chiefly gas) is much more widespread in continental Europe. Again, this was very much a 1970s thing, But now many of these projects are being converted to run on green energy sources e. g. biomass, often in Combined Heat and Power (CHP) plants. CHP coupled with district heating (DH) is seen as efficient way to deliver heat on a community scale. By contrast, individual domestic micro-CHP units and heat pumps are usually much less efficient.

There are also some large community DH schemes using very novel sources. For example, in a long-standing major project in Sweden, about 60% of the total energy input for Stockholms Central Network is provided by the Ropsten district heating plant. This uses the sea as a heat source, harvested by series of 6 large 180MW (e) heat pumps with a total heat supply capacity of 420MWth. They are used for base load production, along with biofuel-fired plants (total heat capacity 200MW). Oil-fired plants are used in times of high energy demand only. The complete plant has the capacity to operate autonomously (i.e. just on ambient energy) during spring, summer and early autumn, when large amounts of seawater are used as heat source. Warm surface water is taken during summer. In winter, the water inlet is in 15m depth where the temperature is at constant +3°C.. The plant can also provide district cooling, with a with a 60 MW cooling plant adjacent to the heat pump. See: and

There's a similar system for district heating and cooling with heat in Helsinki in Finland, where a large heat pump plant produces district heating with capacity of 90 MW, as well as cooling with an output of 60 MW. The plant is in a rock cave excavated under a park. In the winter, the heat energy is taken from purified wastewater led into the sea from the central wastewater treatment plant. Then the heat pumps are used only for district heat - the energy for district cooling is obtained In summer, heat is taken from the return water in district cooling, when the heat pumps supply both district heat and cooling. CO2 emissions from the heat pump plant are said to be over 80% less than from using heavy fuel oil or individual cooling compressors in each house.

Over 93% of Helsinki's heat is supplied by district heating systems and over 90% of annual district heating energy is produced efficiently via CHP. Overall there's 1150 MWe and 3600MWth of CHP/ DH in Helsinki, with one plant linked to the city network via a 30km pipe in a tunnel.

That makes the point that, although we don't all have easy access to the sea as a resource, and we may not want to have large CHP plants inside cities, heat can be transmitted over surprisingly long distances without significant energy losses. For example, in Denmark there's a 17km link from a CHP plant to the city of Aarhus, and in Norway, district heating is provided around Oslo via a 12.3 km pipe from a waste burning plant in the city outskirts But the daddy of them all is in the in the Czech Republic, with a 60km pipe link from the Melnik plant to Prague.

CHP/DH does have it's problems- installing the pipes is disruptive and expensive. But once you have established the infrastructure it can be fed with whatever energy source is currently the best. It is sometimes argued that if you have very low energy using houses, built to Passivhaus standards, then you will not need much energy input, so district heating schemes wont be needed. But an Austrian study disputes this 'especially in blocks of flats, where a lot of m2 are put on top of each other' where 'it is a good idea to supply with district heating, what the building cannot generate by itself.'

Moreover in some situations it is actually cheaper to pipe in heat than to rehab buildings with extra insulation. For example, a study by Orchard Partners for the UK Technology Strategy Board 'Retrofit for Future', comparing Combined Heat (CHP) and Power /District Heating with domestic insulation concludes that, for a typical late 1960s/early 1970s London houses in a terrace of five houses, connection to district heating gives a lower capital cost per tonne of CO2 displaced than alternative insulation measures.

CHP/DH is at long last being taken seriously in the UK, being mentioned as a key option in the new DECC Heat strategy and also in the new Bioenergy strategy. See my last Blog. But we have a long way to go the catch up.

Green Heat 2

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The governments new Heat Strategy review took on board many of the arguments for district heating, and even the use of solar, that previously had been rather marginalised. It identified pathways for the transition of the UK's heat supply to low- and zero-carbon energy sources in the domestic and industrial sectors.

The Combined Heat and Power Association (CHPA) was delighted. It said that 'the Strategy points the way to a major expansion of new district heating networks in towns and cities, driving a multi-billion pound investment programme in green infrastructure and creating an additional 40,000 jobs in construction and engineering'.

The CHPA noted that previous Government studies had suggested that 8 million dwellings could be connected to district heating at reasonable cost, along with a major share of commercial and public buildings, through a 25 year capital programme, investing £2bn p.a. in new district heating infrastructure. Through this programme carbon emissions from heating would be halved and reduced to around 9 million tonnes per annum. It added 'Networks could adapt to obtain heat from gas-fired CHP plant, biomass and biogas, heat pumps, energy-from-waste, solar thermal, along with heat rejected from industrial processes and power stations. This approach, which is commonplace in continental Europe and Scandinavia, delivers reliability and security to energy users and provides a credible and practical pathway to decarbonisation.'

However the policy shift wasn't that large: the Heat Review still backs electrification as the main supply focus, since 'electricity is universally available' and, in well insulated houses, heat pumps can make using it for heating relatively economic. But it did admit that gas grids act as energy stores and are better at coping with variable demand, so that there would, in an electrified system, be more need for storage and demand management, as well as a lot more green generation capacity- almost double the present amount, given electrification of transport as well! Basically from nuclear and offshore wind, plus gas CCS.

Even so, it looks to biomethane and hydrogen, as new fuels, sourced from biomass, that could be used for heating, although it warns that biomass resources will be 'constrained and contested' and probably best used for industry and transport, where higher energy intensities are important. And, a little provocatively, it says large-scale biomethane injection into the gas grid is not realistic 'when efficiency losses are taken into account'.

So, apart from some direct use by industry for process heating and for local district heat networks, it sees gas delivery on a national scale is being phased out, with cooking being done by electric hobs and perhaps induction heaters. A big change for many people. Interestingly, micro CHP is seen as just a transitional option, but solar heating is seen as valuable, especially if combined with interseasonal storage, implying large scale 'heat accumulators' /community heating systems. The industry section is useful, with, in addition to improved process efficiency, gas and biomass CCS seen as a possible option.
Overall interesting then, still wedded mainly to electricity, plus some heat networks. But there are few actual commitments or future supply numbers, just a general plan: a full policy is promised within a year.

Things do seem to take time! The Renewable Heat Incentive for example- which was meant to start the ball rolling. It was set up in two parts, with support of larger business schemes already established, along with an interim domestic-scale grant competition, the Renewable Heat Premium Payment scheme (RHPP), offering one-off payments for homeowners wishing to install green heating systems. DECC had been expected to launch the full domestic RHI in October this year, alongside the Green Deal loan scheme, but it has now decided to delay it until summer 2013, and will instead inject an extra £10m into the budget for the interim RHPP, taking it up to £25m, while reviewing cost control measures.

After its run-in with the PV solar Feed-In Tariff, the government is clearly worried that the projected costs of the RHI scheme, which unlike the FiT, will be met out of government funds, i.e. from taxes, will need to be controlled and kept below the fixed £860m budget. So it's launched proposals to carefully manage the RHI budget. For the existing business scheme, as a temporary measure, it will suspend registrations at one month's notice once 80% of the budget has been allocated. DECC said it will introduce proposals for a permanent cost-control mechanism by the end of the financial year, which could see tariffs fall in line with increased uptake.

Meanwhile, under the new extended RHPP, for the first time, communities seeking to install renewable heating systems will be able to take advantage of the scheme, with around £8m of the budget set aside for local projects. DECC has also earmarked £10m for social landlords to upgrade heating systems, after the social landlord competition last year received such a strong interest that DECC increased the initial £3m budget to £4m.

The Government said it wanted at least 25,000 households to take up RHI offers in the first year. So far, under the first phase of the RHPP, £4.8m has been cashed in by housholders, and 37 social housing schemes have also registered But, given the new review, Gaynor Hartnell, Renewable Energy Association CEO, feared the market will be killed off before it even starts: 'To launch an official consultation on bringing the shutters down, having only just fired the starting gun on the RHI, is premature to say the least'.

Some of the heating issues were followed up in the subsequent DECC, DEFRA and DfT Bioenergy strategy, which backs the 'use of biomass to provide low carbon heat for buildings and industry (process heating), through either biomass boilers or through use of biomethane'. It adds 'Use of recoverable waste heat from low carbon power generation or industrial processes is also an important component of this pathway', noting that 'combined heat and power generation offers more efficient use of the biomass resources and should be promoted where possible'.

It also notes that Bioenergy carbon capture and storage (BE-CCS) offers net carbon removal from the atmosphere or 'negative emissions', which 'could then be used to offset fossil fuel emissions from other harder to decarbonise sectors. This makes BE-CCS an exceptionally valuable technological option'

The Combined Heat and Power Association was again delighted, noting that the stress had shifted to the use of heat networks rather than individual boilers to provide domestic heat, and the recovery of waste heat when used in an industrial setting.

It does seem that, for once, new ideas are beginning to be listened to. I will be exploring some of them in my next Blog.

Green Heat 1

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I have often been less than impressed by reports from the Royal Academy of Engineering (RAE) , which usually seems to take a conservative line on energy issues, but their new report on heating for buildings seems overall very well done, although with lapses. It makes the sensible point that we need to deal with the building envelop first, but also notes that most of the houses that will be lived in by 2050 have already been built, so we must look to remedial measures. It also notes that 'Manchester isn't Leipzig', and looks at patterns of heating need and perceptions of comfort. It assumes we are talking about well insulated buildings, and familiar levels of comfort, and it reviews the energy supply options for supporting that.

It sets the scene by pointing out that 'If space heating could be decoupled from water heating it would change the selection criteria for heating appliances and boilers. There would no longer be a need for the heating system (as opposed to the hot water system) to be on standby during summer months or to be capable of operating at a sufficiently high temperature to prevent Legionella developing in water systems. All domestic heating is currently thought of as low-grade heat requirement, but there is a case for distinguishing space heating as low grade and hot water as medium grade. A policy for heat should separate these two different uses'.

It looks at heat pumps as a possibility, but is not too convinced. 'While the general reduction in carbon intensity of grid electricity makes the use of electric heating (direct or via a heat pump) more attractive, peak heat loads tend to coincide with peak electricity loads. There is, therefore, a significant likelihood of heating demand being met by high carbon electricity generation brought onto the system to meet peak loads over and above the capacity of low carbon generators'.

It goes on 'Air source heat pumps have been rising in popularity for new build in the UK, but this is partly an effect of the way in which electrical energy is treated in the regulations that makes CO2 targets more lenient than for gas systems.' While it admits that 'Air source heat pumps integrate well with well insulated dwellings, if properly sized and installed,' and it suggests that 'micro-CHP complements and could balance some of the properties of heat pumps', it also notes that 'several reports discuss inadequacies of the application or system engineering in heat pump installations. It is clear that heat pumps are not forgiving if installed inappropriately.'

By contrast, it's much happier will larger-scale communal system. 'Communal air source heat pumps are an interesting area of development with some new configurations of systems coming to market. Central systems may be more efficient and are likely to offer much greater energy storage than do systems designed for individual household'.

It adds 'Larger district systems, incorporating a CHP facility and providing heating are significantly more efficient than domestic level installations. This is because waste heat can be used in district heating after it has generated an element of electricity. Such district heat is therefore always of significantly lower CO2 emissions than any heat only production utilising the same fuel'. And that, it seems, includes domestic scale heat pumps.

The RAE does seem to been moving towards community- scaled system across the board. However, it is less happy with renewables. Although it sees some potential for bioenergy e.g for CHP/District Heating , it is not very impressed with solar, and overall treats renewables as problematic in terms of grid power supply, reverting to the traditional RAE line on the problems of intermittency and the delights of nuclear: 'During the summer months, most of the night-time load could be provided by nuclear power with renewables providing additional power during the day', while in winter 'we would need sufficient renewables to guarantee 40GW during the evening peak. As wind, tides and the sun are intermittent, that would require significantly higher installed capacity of renewables or thermal back-up capacity, much of which would be unused for long periods in the summer' making renewables uneconomic.

Nevertheless, it does look at smart grid /load management options which might change the situation radically, helping to deal with intermittency. A bit grudging, but at least there is now some recognition that a new interactive supply and demand system might be viable. It's taken decades to get the community CHP/DH message across to the traditionalist engineers, so maybe it's too early for idea of smart dynamic grids to have got through! And it may take even longer for them to give up on 'baseload' nuclear, which they still see as essential, rather than as getting in the way of a more interactive flexible system based on renewables ( which is the view emerging from Germany) .

However, as far as CHP/DH in concerned, the RAE is now full of praise. It says that 'CHP plants, biomass combustion, and heat pumps are more efficient, reliable and cheaper at scales larger than a single dwelling. The costs of large scale heat pump installations per kW are a quarter of that for domestic-scale installations.' It adds that 'it is more efficient to use the available skills for fewer large systems than for many individual units', and that, since energy storage will be needed 'district heating systems have another important benefit - the mass of water in the underground pipes provides a heat store that evens out daily peaks and troughs in demand. This can be supplemented by hot water tanks to increase energy storage'. And taking it one step further, it points out that 'well insulated hot water tanks or underground inter-seasonal thermal stores will be simpler to provide on a community basis given the small (and reducing) size of most UK homes'.

Some sense last! And DECC seem to be taking notice, in their new Heat strategy- see my next Blog.

'Heat: degrees of comfort?' Royal Academy of Engineering

The Climate Change Committee's report on bioenergy earlier this year was somewhat more cautious than many previous studies, arguing that, at best, the UK might only get 10% of its energy from bio-source by 2050. The CCC saw bioenergy as a scare resource, with significant constraints, not least land use. This of course is a global issue, with for example, in terms liquid biofuels, there being many concerns about the environmental and social impacts of large plantations around the world. It's not just direct land use, it's the impacts of land use changes ('ILUC') that matter, which CCC say must be included, though they are hard to assess. But if at least a 50% emission reduction, below that from fossil fuels, is set as a target, there's less room for manoeuver.

When it comes to solid biomass for heat and power production, things get a little easier in terms of land use. CCC say 'Our core scenarios focus on the use of abandoned agricultural land', with a range of energy crops being viable: 'We assume in the longer term dedicated energy crop feedstocks are a mix of fast growing trees and grasses, as these crops are potentially more suitable to land of low productivity, have low lifecycle emissions and can be converted for use across the range of sectors'. But CCC see Carbon Capture and Storage as vital in many cases: 'If CCS is not available at the scale envisaged, the amount of bioenergy required to meet the 2050 target would have to be significantly higher than 10% of primary energy demand, and would imply land use change exceeding currently estimated sustainability limits.'

They also warn that 'given limits on domestic supply, much of the forest biomass for power and heat used in the UK will have to be imported'. Nevertheless they feel able to conclude that 'Scenarios for global land use which take account of required food production suggest that a reasonable UK share of potential sustainable bioenergy supply could extend to around 10% (200 TWh) of primary energy demand in 2050. However, it would be unsafe at present to assume any higher levels of bioenergy supply, and even the 10% level might require some trade-offs versus other desirable environmental and social objectives (e.g.through energy crops production encroaching on land of high biodiversity value).' But they want tighter limits: 'the threshold for use of biomass to meet the RO should be tightened to 200 gCO2/kWh. This would represent a significant enough saving relative to gas-fired generation, allowing a margin for emissions from possible indirect deforestation.'

Clearly they do not see biomass as likely to play a major role, although they suggest that there might be range of 'sensible smaller-scale local uses' - such as making use of old cooking oil to run buses, using food or farm waste in anaerobic digestion plants, or using woodchip from tree surgery waste in biomass boilers. Pretty marginal then, with CCC concluding 'The role for use of biomass in heating buildings is likely to be relatively limited in the longer term, given alternative low-carbon options such as air-source and ground-source heat pumps. Where these are not feasible, there may be opportunities for district heating using waste heat from large-scale low-carbon thermal power plants (potentially including biomass CCS) or CHP using local waste or biomass, and for biomass boilers using local biomass in rural homes.'

This may be too dismissive a view. Certainly, in practice, biomass/biogas energy options are still struggling to get going on a significant scale in the UK, with objections still emerging to some large-scale power projects, but some are still moving ahead.

E.ONs controversial 150MW biomass power station in the Royal Portbury Docks, near Bristol, has got the go ahead, despite concerns about its part reliance on imported virgin wood. It will also use dedicated energy crops, and locally sourced waste wood. E.ON has said it would set up a community investment fund, contributing £50,000 per year for charitable and educational community projects in the area, while a further £75,000 would also be set aside to trial green buses and improve cycle routes in the area.

However, E.ON told BusinessGreen that it was reviewing its plans for this and other renwable energy projects, in light of proposed changes to subsidies offered under the government's Renewable Obligation scheme. Drax also seem to be having second thoughts again about their biomass co-firing projects, complaining that there was not enough RO support

Meanwhile, Sheffield Council is looking at plans for a £20m waste wood CHP project in the Holbrook area , following on from the agreed E.ON's £120m 30MW waste wood biomass plant on the site of the old Blackburn Meadows power station next to the M1, now under construction. In addition, RES has plans for a 100MW biomass plant in Northumberland on Blyth River.

An energy from waste/biomass complex has also been proposed for the Ince Park development located at the Manchester Ship Canal, as a joint venture between Peel Environmental and Covanta Energy. Construction of the EfW facility is set to begin soon aiming for operation in 2015. Peel Energy has also got planning permission for a separate 20MW biomass energy facility on the site, with construction scheduled to start early next year. Plants like this, which involve combustion, are often opposed by environmentalists due to possible emissions (especially if wastes are used) and also the land-use/ biodivesity implications of large scale biomass growing/importation

In Wales, in a novel project which should avoid these issues, BiogenGreenfinch have been appointed by Gwynedd Council as the preferred bidder for the construction of a new green energy plant which will take council collected food waste and turn it into renewable energy via Anaerobic Digestion. The new AD plant, which should be running soon, will process around 11,000 tonnes of food waste each year; converting it into renewable electricity and biofertiliser for use on nearby farmland. The food waste will be collected from local homes and businesses via a collection scheme run by Gwynedd Council. The new plant will replace the existing landfill site currently situated in Llwyn Isaf and should play a major role in helping the Council meet their statutory recycling targets. It will be the second waste-fed anaerobic digestion plant built in Wales, following the construction of the Premier Foods plant last year near Newport.

In this case, the biogas is burnt to produce electricity, but AD biogas can also be added to the gas main, with, despite CCC's rather negative assessment, the prospects for 'green gas' from waste AD being increasingly seen as a new possible direction for green heat supply-in Germany especially. For more:

While CCC may be a little sniffy about biogas, the new DECC/DEFRA/DfT Bioenergy Strategy is a lot more positive, as is the parallel DECC Heat Strategy. Although they do not see biogas playing a role in domestic heating directly, they do envisage biomass and biogas being used for community heating via CHP plants linked to district heating networks. I will be exploring this, and the green heating options. in my next few Blogs.

CCC report: