Professor Jim Swithenbank FREng, PhD, DSc (Athens), DEng (Sheffield) Professor of Chemical Engineering at The University of Sheffield, talks about Renewable and Alternative Energy Technologies with Robin Saunders - 4th August 2003

 

Robin Saunders: Perhaps we can start with the Walter Ahlstrom Prize awarded to you by the Finnish Academies of Technology: what was the citation for the prize in your case, and to what extent is that prize normally given for work on renewable energy?

Jim Swithenbank: The citation is for research and development work on fluid flow, combustion and the environment, and as an inventor of laser diffraction particle sizing and the Fluent CFD code. The prize is normally given for advances in engineering, particularly in the context of inventiveness.

Robin Saunders: Many congratulations. In recent years your expertise and energy in these areas have been particularly applied to combustion processes in municipal waste incinerators and to their improvement. How did you get started on that?

Jim Swithenbank: It really goes back to the energy crisis of 1972/73 when the price of oil was doubled. I recognised that we could obtain energy from other sources such as waste heat from industry and so on; and then I discovered that the major source of this kind in Sheffield was heat from the municipal incinerator. We therefore devised a district heating system based on that source of heat. I soon realised that the incinerators of that time were little more than covered bonfires. They had not been given the scientific attention that they deserved, so it was a seriously neglected topic in combustion engineering.

Robin Saunders: So continuing with some details about waste incineration: How significant would you say is the potential contribution of waste incineration to the needs of the world in terms of Energy supply?

Jim Swithenbank: A rough estimate is that about 10% of the energy used in the world could be obtained from waste processing plants such as incinerators.

Robin Saunders: Does this produce a contribution to global warming, or is it actually beneficial from that viewpoint?

Jim Swithenbank: Yes it is indeed beneficial. The material in waste from which we extract the energy largely consists of things like wood and paper, in other words biomass. When you burn biomass, it does not make any net contribution to carbon dioxide in the world. The saving in the UK, for example, could be approximately 5 million tonnes of carbon dioxide per year compared with using fossil fuels.

Robin Saunders: That sounds good. So should we be incinerating all our waste, or just part of it?

Jim Swithenbank: A part. We feel that the problem of waste disposal needs a parallel attack on several fronts, and there is not one solution. In Europe we need about 30% of the material to be recycled, about 30% composted, and about 30% used for energy from waste by incineration or gasification or perhaps pyrolysis; for the foreseeable future there will still be about 10% of residual material which needs to be land filled.

Robin Saunders: So incineration sounds important, but it does seem to have a bad press with the UK general public just now (perhaps orchestrated by a few extreme environmentalist groups). To what extent is this justified?

Jim Swithenbank: Well, first of all I'd like to say that I'm in full agreement with the green objectives. I regard myself as very much an environmentalist who is actually trying to do something about this problem. However, the concepts put forward by the extremists such as zero waste are just beyond our capability in the foreseeable future and targets such as that can lead to a loss of credibility of the extremists.

Robin Saunders: What do you see as being the real problems with incineration at the moment, and are they actually being solved?

Jim Swithenbank: The big problem is public perception. The impression given is that incinerators are a major source of pollutants; in fact they are an almost negligible source of pollutants. Take for example dioxin: only 3% of all the dioxin emitted in the UK comes from the incinerators. The bonfires on November 5^th generate more dioxin than all the incinerators do in a year! The oxides of nitrogen in towns don't come significantly from the incinerators but from cars. Unfortunately there is a misrepresentation by the media of the problems and of course this influences the public.

Robin Saunders: Now, is this particularly a UK effect, or are developments and attitudes different in the rest of the EU?

Jim Swithenbank: Certainly the attitudes are very different in the rest of the EU. For example, in Denmark there is strong pressure from environmentalists to extract the maximum energy from wastes, and it has long been illegal to bury burnable wastes in many countries such as Denmark. Austria, for example, is years ahead of us in terms of recycling wastes. However they are currently building two new incinerators to handle a proportion of the waste that cannot be effectively recycled in the Vienna region.

Robin Saunders: You mentioned Biomass just now, and that is fully recognised as a form of renewable energy. Does the combustion of Biomass bring the same problems as with waste, or are there special avenues to be pursued there?

Jim Swithenbank: To a great extent the problems are similar. However, biomass contains things like alkaline metals and technically we have to handle the associated corrosion problems. So far as cleaning flue gas is concerned, I don't think most people realise that technically we can clean these gases to any required level. We have the technology, and in general we can achieve as low a level as we can measure. However, the costs rise dramatically as you try and get cleaner and cleaner, so a sensible economic balance has to be derived.

Robin Saunders: So really Biomass and Waste have exactly the same problems?

Jim Swithenbank: What I'm trying to portray is that, yes, they both have similar problems but these problems are quite soluble.

 

Robin Saunders: Leaving incineration for the moment, I think you also have interests in a wide range of other forms of renewable and alternative energy (RAE). Where do you feel you have made a particular contribution?

Jim Swithenbank: To some extent our interest goes back to work we have done on general processing technology. The design work involves mathematics or modelling - allowing us to take almost any industrial process and optimise it - and particularly flows through wind turbines and underwater power production systems can be helped by the sort of technologies that we have developed here at Sheffield.

Robin Saunders: And is this particularly using Computational Fluid Dynamics for instance?

Jim Swithenbank: Yes we have specialised and furthered that discipline, and indeed we are still developing these topics with particular emphasis on the processing of materials like Biomass.

Robin Saunders: Looking at the range of RAE, which technologies do you think should be supported first and most strongly in different regions, starting with the UK?

Jim Swithenbank: Well, as you know there is a recent government review of the situation, and as a consequence wind power and some of the renewables are now getting additional attention. However, there are limits to the proportion of our energy needs that it is practical to take from these sources. Those limits could be somewhere between 10% and 20%. That still leaves us with a major problem of providing energy for the future. You could regard nuclear power as an alternative energy source to some extent, because as you know this does not generate carbon dioxide as one of its problems.

Robin Saunders: Is the situation different in Europe?

Jim Swithenbank: The priorities in Europe are slightly different, because the UK has a lot of seafront, and therefore we have the opportunity to use wave power and tidal power and so on. This is rather better for us than for most of Europe.

Robin Saunders: What about the world as a whole?

Jim Swithenbank: Well, one big problem in the world as a whole is waste management. That problem is becoming more serious, particularly in the developing world, and we're interacting with many developing countries to try and help them through this great difficulty.

Robin Saunders: So that is clearly a new area of collaboration. Are there any other collaborative mechanisms we need to get into place in this field?

Jim Swithenbank: Yes, I think photovoltaics is one of the most challenging topics (and this must be associated with hydrogen storage) because essentially it allows a nuclear future relying on the sun. The sun is a big nuclear power station, it leaves all its waste out of the way of the earth, it transmits the energy pretty cleanly through radiation to the earth and there's plenty of energy there. The problem of course is recovering that at an economic price and associating it with hydrogen storage because photovoltaics only work on a diurnal basis.

Robin Saunders: Looking at current commercial developments, the most significant RAE source being implemented in Europe appears to be Wind Power (dominated in terms of national investment by Germany and Spain). How far do you think we can go with this, and do you foresee particular problems?

Jim Swithenbank: There are certainly problems; essentially you've got a fluctuating supply and lots of independent sources which is quite distinct from the traditional large power station policy of the UK. That can lead to system stability problems and it also leads to a cost problem because you need standby power generation to make good the gaps in the power delivery from a renewable energy system such as wind. So there are limits that are currently estimated at around 15% of wind power as a practical proportion of a total power system.

Robin Saunders: Photovoltaics (PV) came up just now, and the UK government is offering 50% grants to anyone wishing to install a Solar PV system, but few have taken them up. Do you think this is the right technology to stimulate now?

Jim Swithenbank: As I just mentioned there are tremendous opportunities for photovoltaics in the long term, so yes it is the right technology to stimulate. However, the costs are still such that people are not very keen to take the 50% grant. But if we regard photovoltaic cells as part of the cladding of the building, then that could help to defray the costs.

Robin Saunders: Do you think the enormous energy available from ocean waves and tides will be successfully harnessed on a significant scale in the foreseeable future?

Jim Swithenbank: Tidal barrage schemes are attractive at a few sites, but there is an environmental trade-off to consider. Ocean waves offer power at up to 70 kW per metre of sea front, but this is only accessible at remote regions of the UK. The problems of transmitting the energy underwater and the power losses between the North of Scotland and the South East are very severe.

Robin Saunders: Nuclear Power has been a major baseload generator of electricity in the past, and still is in a few countries. Do you think it will be successful in improving its image in time to return to this position in terms of, firstly, storage of Nuclear waste?

Jim Swithenbank: Nuclear power provides about one third of UK electricity at present, and as old stations close, this cannot all be replaced by winds and waves. People will moderate their views when the lights go out! However, the problems are the waste and here one of the key factors is volume reduction of the waste. We do now work in the area of reducing the volumes of some of the waste material from nuclear plant.

Robin Saunders: The hidden costs, which has really caused problems for instance for British Energy, are the decommissioning costs. How do we deal with that?

Jim Swithenbank: There is probably a greater need for cost control in this area but I'm not an authority on that particular topic.

Robin Saunders: And the third problem which worries people is whether Nuclear Power can be safe from operational failure or military attack.

Jim Swithenbank: Well, military attack can affect all sources of energy, for example long distance gas pipes can be attacked by militants of one form or another. There are also prospects for thermonuclear power, which could be safer, and in this field we are already working on the recovery of Tritium which is part of the process in a thermonuclear power station.

Robin Saunders: Do you think there will be significant new developments in Nuclear Power? You have already referred to Tritium in the context of the JET fusion project, but there could be useful developments in fission technology. Will this happen in the UK?

Jim Swithenbank: Yes, in due course we will probably have breeder reactors. However, largely due to popular pressure there is no serious government commitment to Nuclear Power at the moment, but as I have already commented, in view of the threats of running out of power, attitudes will change very rapidly.

Robin Saunders: And do you think these attitudes will also change in Europe, where Germany has abandoned nuclear power but France relies almost entirely on it?

Jim Swithenbank: Well, I suspect that there will be an interim period where the deficit in power in the UK will be met from nuclear power in France and at that point people will say "Well, why don't we put the nuclear power stations here?"

Robin Saunders: And what about the rest of the world - are there different problems there?

Jim Swithenbank: Yes, very much so. I am quite concerned about a safety problem when a nuclear plant is not operated properly or operated by regimes who have different motives.

Robin Saunders: Finally, a question particularly about the UK, but which also affects Europe as a whole. The Institution of Civil Engineers has recently published a report predicting that in 20 years time the UK will be suffering from severe cuts in supplies of electricity and natural gas as a result of being at the tail end of a very long gas pipeline through Europe from Russia and the Middle East. Do you think that is a good prediction?

Jim Swithenbank: There is no doubt about the prediction. We are heading for a serious problem with electricity supply and equally security of supply is very important, so to rely entirely on those gas pipes, I think, would be extremely risky. We need also the opportunity for local embedded power, many more smaller stations in which we can exploit the combined heat and power opportunities. We are really wasting about half of the energy and the fuel by not exploiting district heating or local heating from the electricity generation industry, so I believe that embedded power is the name of the game in the future.

Robin Saunders: Thank you, Jim, for a most interesting and wide ranging discussion.