My Lords, as we have been reminded today and, indeed, in a previous session of the Committee, an installation providing an intermittent supply of electricity cannot be expected to stand on its own. It must be accompanied by an ancillary installation designed to supply power when the primary installation cannot provide enough. This can be either a storage system that can capture the power of the primary installation when it is in excess of the current demand, or it can be a means of importing power from a region where it happens to be in surplus or from another power plant that can be deployed rapidly to meet the deficit. The latter is currently the most common recourse and the ancillary plant is likely, nowadays, to be an open-cycle gas turbine installation.
In that case, given that the plant has a significant carbon footprint, it is liable to subvert the virtue of emissions-free renewable generation. For that reason, we ought seriously to consider other options. In fact, it has been asserted that the upper limit of the proportion of a nation’s electrical power that can reasonably be expected to be supplied by intermittent renewable sources is about 20%. This figure is well within the aspirations of the European Union energy directives. The EU aims to get 20% of its energy from renewable sources by 2020. Whereas renewables include wind, solar, hydroelectric and tidal power as well as geothermal energy and biomass, we imagine that the preponderance of the power will be from wind turbines.
Let us put aside the question of importing power from afar, which was discussed yesterday in Grand Committee, in order to concentrate on the matter of energy storage. There are two principal means of energy storage that appear to have the greatest potential for development. The first to be considered is a system of reservoirs and dams. At times of low power demand, water can be pumped up to the reservoirs. When demand peaks, it can be released and passed through turbine generators. Approximately 70% to 85% of the electrical energy used to pump the water into an elevated reservoir can be recovered, so this is an efficient affair in terms of energy conservation. The technique, so far at it has been pursued, has also proved to be a cost-effective means of storing large amounts of energy, but high capital costs are entailed in creating such facilities, and they depend on the existence of an appropriate geography.
The most visible leading example of pumped storage in the UK is the Ffestiniog reservoir and dam in north Wales. One of the largest facilities, which is also the least visible, is in at Dinorwig, in north Wales, where a huge reservoir sits in a hidden cusp in the mountain. There is currently a peak capacity in pumped storage in the UK of around 2.8 gigawatts, which is about half the installed capacity for wind-powered generation. There is potential for an increase in capacity, albeit that the associated costs are uncertain. The Department of Energy and Climate Change conducted a hydropower resource assessment for England and Wales in 2010 but not, it seems, for Scotland, and there is much that needs clarifying.
It should be noted that, in the UK, the volatility of electricity demand is greater than in any other country. The reason for this lies in the electric kettles that satisfy the tea drinking urges of our citizens, which are closely linked to the evening schedules of our television programmes. Much of our pumped storage capacity is devoted to meeting the resulting spikes in electricity demand and the reaction of the system to the conditions of demand can be almost instantaneous.
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The next means of storage to consider is one with a vast potential. It is based on the production of hydrogen by the electrolysis of water, which is most efficient if conducted at high temperature. The energy efficiency of this chemical means of energy storage is low compared with pumped storage, but I believe that, in its various forms, it represents the best way forward. Currently, 48% of global hydrogen production is from natural gas, 30% from oil and 18% from coal. Water electrolysis accounts for only 4%. These facts reflect the thermodynamic constraints and the consequent economic choices, which are made within the context of the costs of the feed stocks and the energy. The advent of hydrogen-based storage will, therefore, depend on the availability of abundant supplies of energy and the rising costs of hydrocarbons. I shall deal with the question of the supply of energy later.
There are both direct and indirect uses of the energy stored in hydrogen. The direct uses are in fuel cells and combustion engines. Fuels cells, which nowadays represent a mature technology, pose high capital costs and require a supply of hydrogen of the highest purity. It is probable that combustion engines, both turbine engines and Otto cycle engines—that is, pulsed combustion engines analogous to petrol engines—will eventually predominate.
Hydrogen might also be used, as it has been in the past, to produce synthetic fuels, either synthetic petroleum or so-called synthetic natural gas—that is something of an oxymoron. These are ways of eking out the supplies of hydrocarbons but, on their own, they do not represent a way of reducing emissions of carbon dioxide. However, it is possible to establish a closed cycle whereby methane could be synthesised from carbon dioxide and hydrogen and burnt to produce water and carbon dioxide. The cycle would be closed by recapturing the carbon dioxide and using it to generate a further supply of methane.
There are some fascinating technical opportunities, and we ought to be devoting considerable resources to research and develop some of them. Two things are clear. The first is the need for a strong governmental role in research and development if the opportunities are to be grasped. The second is that most of what is envisaged will require ample supplies of energy. Renewable sources of energy can go only a small way towards fulfilling the requirement. We shall need to resort to nuclear energy to provide ample supplies of electricity and hydrogen.