Steady Current

Many years ago I was talking with a family friend at a party, an economics professor at Middlebury College named Klaus Wolff. I was in high school and the U.S. was in the middle of the energy crisis of the 1970's. Professor Wolff assured me that the next great and world changing inventions in energy technology would be in the field of energy storage, not energy production. I think that history will prove him right, although more in terms of the problem than the solution.

Our planet faces the imminent decline of the rate of production of oil, coal, natural gas, and perhaps even uranium. As we extract less and less energy per year out of the ground we will have to use less and extract more out of the sky. That is, we will become more dependent upon direct and indirect solar energy, whether that is from photovoltaic panels, solar hot water collectors, wind turbines, hydroelectric plants, biomass fuels, or wave and tidal power.

The problem with these burgeoning forms of energy collection is that they are variable and intermittent. The sun and wind come and go as they will, and are only very roughly predictable in their intensity from day to day. Hydroelectric production varies from season to season and rainstorm to dry spell. Tidal power is eminently predictable, but has pauses at its high and low points. We are used to tapping into millions of years of stored solar energy in the form of fossil fuels, which allows us to have a continuous flow of power into our homes and businesses. When the sun isn't there, it's called night, and nobody thinks anything of it. When the electricity isn't there, it's called a power outage and the phone rings off the hook at the local utility.

In the case of heating with biomass, the storage of renewable energy is no big deal. Lots of houses in Vermont and elsewhere have a big stack of firewood in a shed or under some tin roofing out back. In the case of electricity, it is a huge problem. Batteries for storing solar electricity are large, heavy, expensive, and all too mortal. Our regional power grids are far too large to use batteries as a solution for intermittency. There is no storage in the system. At present we use natural gas fueled turbines to adjust to the variability in electrical demand. The multi-megawatt output of these turbines is ramped up and down as millions of people push down the toast in the morning or turn off the lights at night.

As natural gas production drops off in the near future (See my earlier essay Gloom and Sunshine), the cost of this conveniently adjustable natural gas fueled electricity will become prohibitive. What then? Coal and nuclear power plants do not adjust their output efficiently or quickly, and those fuels will eventually, inevitably become scarce themselves. We need to go elsewhere for our variable power needs.

Several options make sense. The simplest, at least in terms of existing technology, is hydroelectric power. While hydro can't be ramped up beyond the limits of seasonal water flow, it can be adjusted within its limits to a variable demand. There would have to be some financial arrangement between hydroelectric plant operators and utilities to reimburse the operators for unused capacity, but convenience always has its price. In Vermont we have 137 megawatts of hydroelectric power in operation and somewhere between 15 and 25 megawatts of prime hydroelectric sites waiting to be developed. There are many more existing dam sites that could be developed economically in anticipation of increased electricity prices. (There are also 550 megawatts of hydroelectric plants on the Connecticut River that our Governor, Jim Douglas, recently failed to buy. Give it ten years and this failure will be recognized as the lost opportunity of the century.)

Another option is load shedding. Large buildings could have their air conditioning systems placed under joint control of the building manager and the utility. In the event of a high peak load in the summer, the building could have its thermostat raised by a critical degree or two for a critical hour or two in mid-afternoon. Added to a thousand other large buildings with the same system, the savings could shave the top off of an untenable electrical demand. Industries could coordinate the timing of their energy intensive processes with each other and the utility to smooth out the overall power demand curve. A business with enough flexibility might schedule an activity to correspond with a predicted sunny day or windy night. It would be a new way of thinking about business practice and energy use, but a necessary adaptation to the decline of unconstrained fossil fuel supply.

There is one technology that is just appearing on the market that offers great promise. That is Stirling cycle cogeneration. I'll spare you the physics of the Stirling cycle engine, except to explain that it is a 200 year old design that has finally come into its own with the advent of modern high temperature materials and computer aided thermodynamic design. Heat one end of the engine and cool the other and you get power output. The fuel can be anything from diesel to wood pellets. Cogeneration is the practice of burning fuel in an engine to make electricity and then collecting the waste heat to do something useful, such as heating your home. Cogeneration is common in Europe, and less so here, but usually confined to industrial-scale operations. The technology hasn't been available to make small cogeneration economically viable. Enter the Stirling cycle furnace. A homeowner would be burning something anyway, just to heat the house or a tank of hot water. Why not extract some electricity along the way? Such furnace/generator combinations are soon to be being marketed in Europe and Asia. It would make perfect sense, especially if the devices were paired with some hot water storage and the same kind of shared control as the load shedding I mentioned above. A utility could call on a few thousand homes for a few megawatts of instant power, and the homes would get credit on their electrical bill plus a tank of hot water.

It's not a matter of choice, actually. As natural gas gets more scarce and expensive, power producers and consumers will have to get more imaginative about balancing the ever changing supply and demand. Eventually we will either have to change our expectations about continuous electrical supply or manage the challenges of entirely renewable generation.

Comments

[Clayton Yaun BSIEN]

Very Good article.

I am a alternate energy homebuilder/Industrial engineer and have been waiting until I can get my hands on a stirling engine that I can build reliable offgrid homes in the mountains. There are non available in the USA. I'd even buy a 10 to 12 KW unit and do cluster homes if it were available (one like Sandia national laboratory is experimtneting with for the project in the California desert) My point is this, there is demand right NOW for these smaller units. I would be the first in line. As a bonus consider this....Our grid is vulneralbe to terrorist attack and is a wornout infrastructure anyway I hear. I like the idea of decentralizing electricity generating sites making them smaller, better and more numerous with an inherent safety redundancy.....build a more localized grid with each home as both a user and contributor. Makes sence to me !

Clayton Yaun