STEAM POWER FROM THE EARTH


| September/October 1981



Steam well demonstration

108 Garfield Avenue, Madison, New Jersey 07940

Our preoccupation with soaring energy costs and declining supplies of oil have focused our attention on possible alternate sources of energy. The media are continually calling our attention to undeveloped resources such as solar and geothermal energy. The extent of this leads us to wonder just why it is that more is not being done to tap these seemingly limitless reservoirs of power.

For those of us interested in old steam power, perhaps it would be a useful project to examine geothermal steam. At least it has an intriguing name and that might excite our curiosity. First, though, let us examine the very word itself. Geo comes from the Greek meaning earth and, of course, we know that termal means heat. So, there we have 'geothermal' meaning 'earth heat.'

Throughout the world there are many areas of geothermal activity manifest at the surface in such forms as hot springs and geysers.. There are even more widespread areas of subterreanean heat below the surface. We are not necessarily aware that they exist, but they could be tapped through deep well drilling. Also, there is the hot magma beneath the earth's crust with energy beyond imagination ... if we could just get at it. But, let us not befog ourselves with such esoteric sources as the earth's magma and simply grasp that which we can see and feel as we cross the width and breadth of this land. Then let us examine the problems and possibilities of generating steam power from the earth's heat.

There are a few places around the world where one can drill a well not greatly different from an oil well and produce dry steam (Umm, well, nearly dry) for direct use in a steam engine or steam turbine. Probably the oldest commercial installation of this type is in Larderello, Italy, where a 250 kilowatt generator (235 horsepower) went on line in 1913. The largest is undoubtly at the Geysers area in California where presently some 800,000 kilowatts of capacity are in service and more is being added. Up until around 1975 the New Zealanders had operated 192,000 kw at Wairakei Power Station but that is being phased out due to technical and economic problems. In 1970, the author witnessed some field tests of steam producing wells near Reyjavik, Iceland, where power generation was being studied. Around the beginning of 1978 the Icelanders started up a 30,000 kw unit of a planned 60,000 geothermal development. There have been some start-up problems associated with insufficient steam production from the wells and there have been some steam quality problems. But, Unit #1 is pumping power into the national system.

So far, fairly extensive geophysical exploration around the world has not revealed additional reservoirs of dry steam. Generally, geothermal heat is in the form of hot water which can be flashed into steam. And, in order to be hot enough to be useful in generating steam power it must be very deep in the earth. Let us see why this is true. One of the sources that we will want to discuss in more detail as an active power project receives the water at 550cF. In order for water to exist as a liquid at this temperature it must be held at a pressure in excess of 1000 psig. Therefore, it must occur at a depth below the surface in excess of 2400 feet (0.43 psig per foot of water column). Drilling wells to this depth is no great problem, technically, but doing so into a formation at 550°F is. Some of the very hottest oil wells such as in Alaska are not over 180°F. This presents a real challenge.