New energy for old

Over the last weeks and months there has been a number of news items and parliamentary exchanges involving energy matters. Aside from widespread axe grinding, narrow-gauge arguments and superficial proposals, the debate suffers from one major defect: it is being conducted in a vacuum. We are caught between a ghostly energy policy, with a gestation period at least twice as long as that of an elephant, a draft strategy for sustainable development that gives energy a back seat, and ministers, shadow ministers and authorities often singing divergent tunes.

Perhaps one needs to establish some outer limit to this debate. We have little or no chance that in this 21st century we will be able to replace all our fossil fuel use for energy generation. So our best effort should be directed at an increase in efficiency at all stages of the energy cycle, from generator to consumer. A start has been made but it seems slow and hesitant, perhaps more concerned with being seen to be doing something than with a concerted programme. No results have been published, despite our subscription to international conventions requiring this type of information to be made public.

On renewable energy, a line that should be rejected from the start is the one that argues blindly for one "solution" to our energy problems. There is no such panacea; we need to look at all possible sources on technical, economic and other grounds and extract from each what we can. At present (and on different time and energy scales) we can hope to utilise the sun for water heating, air conditioning, electricity and fuel (hydrogen) generation and wind for electricity and fuel generation.

Solar water heaters (SWH) are now within reach of most members of our two-car per family population. A Lm70 subsidy towards the cost of a SWH is being offered by Enemalta to new customers; but information on the number of takers is a closely guarded state secret. Backed by other measures - higher electricity rates, proper installation and retrofitting, use of twin-inlet washing machines for good summer utilisation - we have the potential of avoiding around five per cent of present generation (and that at time of peak demand), carrying a fuel cost of some Lm2 million. One aspect that will bear looking at is the integration of solar water heating panels in house structures for aesthetic and efficiency reasons. However, one should not underestimate the importance of trying to match supply and demand for SWH.

Air conditioning partially or wholly directly driven by the sun is an application that for us would combine maximum supply with maximum demand. Good technology is already on the market with large units but is still some time away from house or office units.

The direct generation of electricity by photo-voltaic (PV) panels offers another source of renewable energy where supply coincides approximately with demand. Significant areas of private roof are available, together with large public buildings (airport terminal, hospitals, university) where panels can be set up out of any direct view so as not to mar aesthetics. In new major buildings PV can now be incorporated in façades, in glazing and even as structural elements.

At present, costs are rather daunting for the private individual. PV panels generate electricity when exposed to sunlight; but they do not store it. Whether one goes for battery storage or transfers energy generated directly on to the mains, there are high costs associated with the both generation and storage equipment.

In the case of mains transfer, as one is actually helping the power stations, there is the question of payment for the energy deposited on the grid. In what can be seen as a historic move, Enemalta is offering to discount such units at its middle (domestic) rate of 2.5c; no doubt it will offer something similar to industrial and commercial generators. This constitutes a step forward but not one likely to generate any serious rush to install PV, as long as capital costs remain high and state help with capital cost non-existent.

Regional governments in Italy are currently covering 70 per cent of the capital cost and discounting generated units at the standard selling price. Germany, with its large PV industry, provides 50 per cent of the capital cost, constrains the owners of grids to buy the PV power and to pay small generators 4-5 times the rate for fossil-fuel generated units. This accounts for the very widespread use of PV in Germany.

Wind energy presents us with a somewhat different set of circumstances. It is now a soundly established fact that we have a useful wind resource averaged over the whole year, with low production in summer. The perceived scale of application is different from that for SWH and PV, with a tendency to go for generator units of at least a few hundred kilowatts. This puts wind power out of reach of the individual; it also makes distribution grids the natural repository of wind-generated electricity. That is not necessarily good news as far as we are concerned. With a total generating capacity of 500MW, ours is a small, isolated grid; that makes the deposition on and removal from the grid of significant and variable quantities of energy from wind generators, particularly if it is out of tune with demand, somewhat problematic.

One situation which particularly exercises engineers arises when demand on a small, isolated grid like ours is at a low point but is expected to rise in one or two hours. If your primary units are steam turbines, which are rather slow to respond to increases in demand, these have to be kept running - as the so-called spinning reserve - even if the load on them is very low. Under such conditions steam turbines are rather inefficient; the last thing engineers want to do is to transfer wind-generated energy onto the grid, thus making the load on the turbines even lighter. On the other hand the farm owner would not like to see rotor energy being dumped simply because it happened to come at the "wrong" time.

The steam turbines cannot be switched off as their response time is long and the wind contribution is variable. To keep quick-response gas turbines running in this role is expensive; gas turbines burn diesel rather than heavy fuel oil (HFO). These difficulties are by no means insoluble; but we do need one or two land-based rotors to explore grid connection and buffering problems over at least a full calendar year.

When we have solved the engineering problems, we can then face the closely linked questions of location, space, noise, aesthetics and economics. None of these is trivial; none is insoluble, but they cannot be addressed in isolation. For instance, dismissal of rotor location to offshore, citing lack of space and the examples of Denmark, Germany and the UK, is a common knee-jerk reaction here. Never mind that the countries in question have many land-based farms; that they also have wide areas of shallow (less than 10m deep) sea; that they have well developed industries and policies related to rotors and the distribution and sale of wind energy; that they have few if any grid connection problems. The North Hoyle offshore wind farm (N. Wales, 30 x 2MW rotors) for instance, started supplying electricity to customers in the Manchester area as soon as the last rotor was up. These customers, subscribers to a "green" electricity scheme, were formerly getting power from Scottish Hydro.

We, on the other hand, have no planning, engineering or fiscal policies in place as yet and we have already choked over the prospect of having to follow the universal practice of paying preferential rates for renewably generated power, at least for a start-up period of a few years. So, before engaging in futile arguments, we need to make an urgent start on the engineering problems which, if we cannot solve properly, will rule out the use of wind turbines "on", "off" or "above" any shore.

Marine generation, based on tide, waves or sea currents is being seen as a future contributor to renewable energy. As far as we are concerned, the very small Mediterranean tide rules out any application, while waves and sea currents may hold some promise. The technology is still under development. One marine source that might bear looking at would utilise the temperature difference between surface and deep water; a sort of terrestrial analogue would use shallow rock strata or well water in which to deposit heat energy in summer, some of which can be recovered in winter. Here the technology is well developed, having been applied in several major buildings in Europe; but it is not strictly a renewable energy source but an increased efficiency conventional source.

As matters stand at present we would do best to concentrate on a vigorous energy efficiency drive, accompanied by suitable applications of solar and wind energy. Yet, whatever line we take, it will be neither easy nor cheap.