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Sustainable Infrastructure Investment - the 'Fifth Fuel' - energy conservation

December 10, 2009 by admin

Sustainable Infrastructure Investment

To make a transformation to 100% sustainable energy supply, Ireland needs principally to develop its wind tidal and biomass resources.  The Irish wind resource is large enough for exports to other areas if grid infrastructure and interconnectors are developed. Daily Tidal energy is predictable but intermittent.  Biomass is appropriate for the times wind energy is not available, but this resource is limited, so extensive use would have to be made of the 'Fifth Fuel' - energy conservation.

Energy conservation can be partially self-funding, if mechanisms exist to recover an income stream or a premium from an investment in it. e.g. An addition to an electricity or heat bill can fund better heating controls or insulation for solid walls, and house prices rise with double glazing.  

When the output from more efficient or renewable generation plant is sold for new uses at times, this can introduce additional revenue to fund energy supply and save national carbon and energy security costs.  E.g. Wind energy can be used to displace imported high carbon fuels such as oil and coal used for heating in the domestic sector.  

Reducing emissions with heating loads

Installing more efficient Combined Cycle Gas Turbine plant, running it for longer to recover higher capital costs, and using the additional output to displace residential heating loads can save carbon, especially if using Heat Pumps to displace oil heating:

*UK Grid electricity carbon figures may be higher than local figures.
Generation costs and efficiency figures from Philip O’Donnell Eirgrid 5 Nov 2009

Automatic 'Smart' grid systems can connect and disconnect load to make the most of efficient generation and renewable energy, and can also make more of local grid capacity at lower voltages. e.g. By directing local generation such as smaller wind turbines to local applications such as rural hot water heating or milk cooling without overloading the regional grid, which would already be carrying the output of larger wind farms.

Such systems can also control Combined Heat and Power generators and existing standby generators,1 to act as a Distributed Energy ‘Virtual Power Station’.

1 Ref. Dr Jason Kennedy QUB Electrical Engineering

Using more Wind and CCGT with Heating Loads:

Schematic of using heating loads to avoid wind curtailment. E.g. Night water heating.

Energy is more valuable when it is predictable, and cheaper when it is not.  If this price difference can be presented to customers this opens up opportunities in fuel substitution and energy storage.  Electricity prices are already dipping with wind energy availability, and this could become a barrier to further private investment in wind energy supply unless the demand for intermittent energy can be increased over time.

Presenting variable prices to the market early will stimulate investment and innovation in demand control, energy storage, and fuel substitution, whether this variability stems from wind availability, shortage of fossil generation capacity, or from fluctuations in spot gas prices.  There will be an economic benefit in exaggerating price differences, e.g. By reducing grid charges in periods of low demand, to increase the pace of adaptation and reap longer term benefits such as a reduced need for future network rienforcement.  

A combination of variable or ‘dynamic’ tariffs and automatic controls could ‘flatten’ much of the load profile to increase the proportion of electricity generated using more efficient Combined Cycle Gas Turbine generators.  They could also provide Demand Side Management services to System Operators to help cope with wind variability. If suitable tariffs/ ‘interruptable loads’ are put in place, there is an incentive to install additional heat storage and demand control when installing heat pumps, so that they can contribute to stabilising the grid with higher wind penetrations.  

Illustrative load profile with a Smart Metering/ Smart Grid implementation:


Modern 'Inverter' driven heat pumps can reduce their output on demand.  An automatic ‘Smart Grid’ system could occasionally stop them altogether during a rapid drop in wind energy or in a grid emergency, to give a reserve generation time to start without disconnections.

Sustaining Investment in Wind Energy/ CCGT by Heating Fuel Displacement

Being able to use wind energy to displace other heating fuels used on the island may be very valuable, allowing the wind industry to expand without being constrained by a lack of interconnection,  avoiding a collapse in wind energy prices in 'good' wind years, and providing a steadier export wind profile to enable interconnectors to be financed.  Examples of heating fuel displacement would be to use wind energy instead of oil or coal heating to heat hot water and homes at times. E.g. To heat a coal fired home on some mild windy days, or hot water in summer nights.

Electricity generated using gas at low 'Spot' prices, perhaps arising from ‘Take or Pay’ gas contracts in ‘good’ or ‘bad’ wind years, could also be used to heat homes instead of other fuels, especially if some additions to electricity unit costs were set aside when extra electricity is generated for this particular application.   For fuel substitution to happen in bulk, the final retail price of heat from electricity, including all charges, must be notably lower, at least at certain times. Seasonal and half-hourly wholesale electricity prices are quite different from more stable residential retail rates, so that there are episodes of low wholesale prices that could provide heat at prices competitive with other fuels if low wholesale prices were passed through for a limited period.  Fuel substitution can save a lot of carbon, especially if wind energy would otherwise be wasted.

1 GigaJoule of Wind Energy displaces:

1.  112Kg CO2 if used to displace UK grid electricity
2.  >88Kg* if used with an immersion to displace oil heating at 85% efficiency
3.  264Kg if used with a 300% efficient heat pump to displace oil heating.

*This figure rises where an oil boiler located outside is heating hot water in summer.

One benefit of increasing the demand for 'non firm' or intermittent wind energy would be to increase the economic output of the cheaper to develop onshore wind sites, where the output of turbines is currently capped to make the wind output more constant.

Storing Energy as Heat

Homes in Northern Ireland use 44% of primary energy.  Every home has some energy storage.  Walls have thermal capacity, hot water tanks can store a lot of energy depending on their volume and temperature range, oil tanks and coal bunkers are chemical energy stores that can have their output discharged depending on the availability of substitutes. Water holds a comparatively large amount of heat.  Large thermal storage tank systems heated by off-peak electricity developed by Mr Rice were manufactured in Northern Ireland in the late 1980s.

The time heat can be stored depends on the ratio between insulation and the thermal capacity of a heat store.  A badly insulated draughty house could lose half of its heat in an hour.  A very large hot water tank with lots of insulation can hold heat for hours days or weeks.  Most homes are somewhere between the two extremes. If we get heat earlier than we 'need' it, its value is reduced by heat lost before we arrive to use the heat.  


Depending on the amount of insulation and thermal capacity involved, heat is usually worth something.  Even heat ‘lost’ by a hot water tank is useful as heating for about half the year.

We prefer homes that already have the walls warm, as we sense 60% of our heat from the temperature of surfaces around us, so heat supplied ‘in advance’ can be a comfortable choice, encouraging us to set heating thermostats at lower temperatures than we would otherwise, or discouraging us from lighting an inefficient coal fire.

Want Heat Buy Heat

In Ireland we want heat and buy fuel, usually fossil oil to be burnt in an inexpensive boiler.  Most low carbon energy systems such as heat from power generation, from waste, or from burning wood biomass, meter heat rather than fuel.  Larger sized systems usually have higher efficiencies and cheaper inputs, so have cheaper outputs.  Often it makes economic sense to invest in one larger system and to share the outputs between multiple users.

If we want to reduce our oil and gas imports, it is appropriate to introduce a heat metering infrastructure to the whole island.  This can support the deployment of biomass and combined heat and power systems of all sizes, whether serving 200 homes or two.  The most economic way to introduce heat metering would be to 'piggyback' on an introduction of 'Smart' metering for electricity and water, as electricity companies already have metering and billing infrastructure in place.    

Such a system could also work for heating oil, avoiding the situation where low income households are adding to stress on the electricity system by using an electric fire in peak demand periods because they cannot afford a fill of oil, despite it being better value.  Some local councils and charities have already introduced ‘Oil Stamps’ so that low income households can save for a fill of oil, but this ad-hoc system is not universal, and has administration costs.  Stamps can be stolen, and trying to get extra oil out of an almost empty tank can result in damaging oil spills.

New Building Standards

New Social Housing in Northern Ireland is built to 'Code for Sustainable Homes' standard, part of which is a demanding standard for Carbon Dioxide emissions arising from electricity and heat used in the home.  Recent definitions of the standard have ruled out counting the output of remote wind farms towards the target.  Building Regulations are also based on CO2 emissions, and a revision of these is due.

If the use of stored wind energy for heating and hot water provision is not validated or acknowledged in these standards, a potential source of support for investment in wind will be lost.  There is not likely to be commercial interest in the testing and certification of such systems, as it is likely to be very difficult to generate patent protection for the water tanks etc involved.  Even if testing were complete, Agrement board certification to support widespread deployment costs tens of thousands of pounds.

Solar water heating or imported solar electric panels are relatively expensive and do not relieve fuel poverty efficiently, but are already included in local building standards.

One approach would be to create a 'wind bond' that could purchase a CO2 allowance for a well insulated building with extra heat/ hot water storage provision.  Receipts could be invested in dedicated wind related infrastructure such as wind farm connections or compressed air or pumped hydro-electric storage.

Andy Frew
20 Nov 2009
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