On a large plot of barren desert adjacent to Moshav Ashalim, a remarkable, long-term experiment is unfolding. Three independent consortia, each employing a different kind of solar technology, are learning how to operate their giant power plants as effectively as possible under the constantly changing weather conditions. Each consortium was contracted to build a solar power plant, operate it for 25 years and then hand it over to the state on condition that it will still enable it to generate 95% of the power it did when new.
Contrary to the negative economic image that some people have rushed to give the Ashalim solar project, it is an experiment that, like our country’s attempt to land on the moon, should be hailed as a major Israeli achievement and contribution to humankind.
This has been the unanimous opinion of absolutely all the overseas visitors (specialists and non-specialists alike) I have taken to the lookout hill opposite the Shikun Uvinui thermo-solar field. From that vantage point, one can see all three systems (the Shikun Uvinui solar troughs in the immediate foreground, the glowing Brightsource tower in the distance, and Clal Sun’s sun-tracking photovoltaic panels round to the right). When I give tours as professor emeritus of Ben-Gurion University of the Negev, I usually explain to nonexperts the advantages and shortcomings of each, and the unique importance of having all three solar technologies operating at the same place in the Negev.
Before pointing out the importance of these three solar technologies, it is necessary to explain why no single conventional power-generating technology is capable of fulfilling the two basic conditions that constrain all serious power companies. These are, to provide power 24 hours everyday, and to do so as economically as possible.
This is the reason why the Israel Electric Corporation uses a combination of coal-burning, gas-burning and oil-burning plants, even though each technology on its own has very different economics in terms of plant cost, maintenance costs and fuel costs.
One might wonder why, if this is the case, they do not use only the cheapest, namely, coal. The reason is that to do so would involve the company having to generate huge amounts of power during times when there are no customers to use it, because coal plants respond very slowly to changing needs.
Alternatively, the company could use another type of technology, gas turbines, that can generate exactly the amount of power that is needed at any given moment, but the maintenance costs of such generators would be enormous. The most cost-effective strategy is accordingly to use the company’s different power plant types (I have given here only two examples for simplicity), fired up and ramped down according to a computer algorithm that constantly measures customer needs, taking into account varying fuel costs, and the age and maintenance costs of all plants.
WITH THESE constraints in mind, here’s what solar power could do for Israel in the future, not the least of which is that the goal of pollution-free power-production is worth reaching. Seemingly, the “cheapest” solar technology is an array of photovoltaic panels.
Such a power plant is certainly the simplest to build and panel prices have dropped drastically in the last few years owing to competition among manufacturers for the enormous markets this versatile technology has created (e.g. wrist watches, parking meters, bus-stop schedules, roof-top arrays, and all the way up to multi-megawatt power plants).
But photovoltaic power plants have two drawbacks. First, the panels produce power instantaneously, in quantities that follow the momentary variations in solar illumination. This means that their output cannot, as yet, be controlled.
This situation will change when appropriate storage methods are developed, because storage batteries will allow surplus solar-generated energy to be stored until it is needed. For example, it will enable possibly unneeded noontime production to be held over for use during periods of peak demand on summer afternoons and winter evenings. However, for the time being, such storage is not available. So unwanted peak generation has to be dumped.
By contrast, solar-thermal technology has the important advantage that instead of generating electricity directly, it generates thermal energy (i.e., heat) as an intermediate step. Unlike electricity, thermal energy is easy to store. This enables the electricity to be generated at a more desirable time of day according to needs.
In the case of the trough technology employed by the Shikun Uvinui system, there is a certain amount of intrinsic thermal storage due to the many kilometers of solar-heated oil that is pumped through the vacuum tube which runs along the focal line of the mirrored troughs. This renders the temperature of the oil relatively insensitive to variations in solar illumination caused by passing clouds.
Furthermore, the Shikun Uvinui system can also store part of the collected solar heat in large storage tanks of molten salt, so that it can be used for a few hours after sunset when there is a large mismatch between electrical demand and solar availability.
Another example of solar-thermal technology is the brilliant solar tower of the Brightsource solar-thermal system. The tower is surrounded by tens of thousands of solar mirrors, which follow the sun’s relative motion across the sky, redirecting its rays to the boiler on top of the tower.
That boiler generates steam which is the power source for a turbine that, as in the trough system across the road, generates electricity. One of the advantages of the tower kind of technology is that, depending upon cloud variations and variable electricity demand, the number of mirrors that point at the tower can be quickly varied, so as to regulate the system’s power output.
I have indicated how each of these three systems has a different response to passing clouds: the rapidly varying output of photovoltaic panels; the adjustable output of the solar tower; and the relative stability of solar troughs. Thus, the unique advantage of Ashalim over the other large solar projects around the world is that these completely different utility-scale solar technologies are located at the same place.
Consequently, the data that will emerge when all three systems feed the power grid will enable future electricity planners to develop an appropriate algorithm for operating the three, under all weather conditions, in much the same way that coal, gas and oil plants are shuttled on and off today.
BUT WHAT of the long-term future? With appropriate storage, approximately 90% of Israel’s future electricity needs could be provided by photovoltaic panels, with the remaining ten percent being provided by gas backup – mainly for sequences of cloudy days in winter. When the results of the Ashalim experiment are digested, it is not inconceivable that solar-thermal plants, together with some wind turbines might someday complement photovoltaic plants and render Israel’s electricity generation 100% independent of fossil fuels.
But what about land availability? If each of the 40 yishuvim in the Negev were to operate a 25 megawatts photovoltaic power plant, together, this combined 1000 MW of solar power could generate about 2 billion kilowatt hours of electricity annually, i.e. about three percent of Israel’s present electricity needs.
But what about the remaining 97%? Each 25 MW Negev plant would require about 400 dunams of land. However, as all Israelis know, our little Negev is minuscule compared with the deserts of Egypt and Jordan. Consequently, there would not be enough available land in the Negev (i.e. land not required for other purposes) to enable 100% of our electrical needs to be generated by solar energy here.
However, the peace agreements with our two neighbors have withstood the vicissitudes of politics for decades. So, it is not inconceivable that one day, gigawatt-size solar power plants, each covering some 16 sq.km. and dotting the vast Sinai and Jordanian deserts, could provide copious electrical power for all three nations, and also for the Palestinians.
The West Bank could receive its power from Jordan while the Gaza Strip could receive its power from Egypt. Perhaps with enough electricity to allow full economic development, a future Palestinian administration would consider afresh the advantages of living in peace with Israel.
DAVID FAIMAN, jpost.com