DaveS,

Where do I find his white paper? A search reveals nothing so far.

PeterS

Hi Pierre,

          Using back-up generating plants for renewables is redundant and expensive. It would be much better, where ever possible, to integrate wind with natural gas powered generating plants, at least during the transition to all renewable energy. One way to do that is to have the windmills compress air, and save the heat of compression. That provides energy storage. Then the compressed air is used in the gas turbine, with the result that the gas turbine does not need to consume natural gas during its air compression part of the cycle. As I recall, that can about double the efficiency of the gas turbine, which means a 50% reduction in CO2. The heat of compression can be added to the compressed air before using it in the gas turbine, thus increasing the temperature and pressure of the compressed air.

          Another approach is to use windmills or kites to generate only heat using direct agitation of a heat-resistant substance. Then the heat can be used to create steam for a steam turbine, in conjunction with the usual fuels such as nuclear, coal, wood chips, crop residue, or solar-thermal plants.

          The problem with these options is that it is difficult to locate windmills or energy kites close enough to a conventional generating plant. So it is important for renewable energy sources to be designed in ways that can make integration possible. HVDC lines may make it possible to locate gas turbine generating plants on wind farms (windmills or kites), thus facilitating integration.

          The cheapest energy conversion is to convert wind energy directly into heat because the mechanisms are simple and inexpensive, and the conversion efficiency is, in principle, 100%. The heat-storage medium can be inexpensive, such as molten salts as used for solar-thermal plants.

          Fossil fuel generating plants have built-in energy storage in the form of the fuel itself. Wind energy designers need to think in terms of integrating energy storage with energy production. Direct wind to electricity makes good sense when wind is only a small part of the energy mix. But as its contribution increases, built-in energy storage becomes more necessary.

          The need for water desalination is increasing rapidly. Converting wind energy directly into heat for vacuum distillation might become relatively cheap and efficient. But I don’t have the figures on that. The use of fossil fuels for desalinating water is clearly the wrong way to go. How about an integrated plant that uses stored heat from wind energy to produce steam from salt water -- to generate electricity -- which also produces fresh water? Does the technology exist? I would assume that it exists but that it is still too expensive. Salt corrosion might be the main barrier.

          Our current energy grids discard excess wind energy when supply is high and demand is low. That is wasteful. Amory Lovins has suggested using the batteries of electric cars as a major energy storage medium for renewable energy. (But I consider cars, even electric cars, to be extremely wasteful in themselves – as compared to using a Personal Rapid Transit system that integrates both private and public vehicles.) Should we store energy before or after it is converted into electricity? For the grid, I say before, not after, in most cases so as to reduce costs and increase efficiency.

PeterS

Hi DaveS,

          Since you have explored the idea for years, please explain to me the details of how to couple 100 long pull kites to the generator of a gas turbines so as to maintain the necessary precise frequency required for the AC grid.

          I ask because something I want to build is a number of Bird Windmills all spinning the same generator shaft via jerker lines and one-way clutches on the shaft of the single generator. But I don’t know how to couple the same generator to a gas turbine (unless perhaps, it is a DC generator that does not require a precise frequency to be maintained). So please tell me how to do it.

          It is relatively easy to control the feeding of compressed air into a gas turbine to maintain frequency precision, but it seems quite difficult to control a highly variable mechanical input in the same way. What is your method?

PeterS