"Very large-scale"solar-electric projects in the desert could help fill the world's demand for energy and bring drinkable water to the driest regions at the same time, said Peter van der Vleuten, a member of an International Energy Agency task force, today at the European Photovoltaic Solar Energy Conference.

His presentation was part of a report by the IEA Photovoltaic Power Systems Programme's task force on so-called Very Large Scale Photovoltaic Power Generation Systems, which are projects that span a range of megawatts to gigawatts in size.

These gigantic projects make sense because "the desert regions receive more solar energy in six hours than the world uses in a year," van der Vleuten said. Also, most desert regions are surrounded by salt water and are facing serious water crises, he said.

How serious? Some 1.2 billion people - 20 percent the world's population - have no access to clean potable water, leading to 12 million deaths every year, and these numbers will grow even more dire, he said.

Desert regions could become energy-independent, export power internationally, boosting their economies, and also have enough left over to support desalination.

Some 80 to 90 percent of the cost of desalination, which would make salt water drinkable, is energy, he said.

"It is a basic right that all societies and human beings should have fair access to energy markets, bearing in mind that energy production and consumption must be sustainable for future generations," van der Vleuten said, quoting the address by Prince El Hassan bin Talal of Jordan at last year's World Energy Dialogue.

All very well, but many in the industry today believe that photovoltaic solar panels are far too expensive to make sense in these large-scale projects, and think that concentrating solar-thermal power, which uses the sun's heat rather than its light to deliver electricity, makes more sense in utility-scale applications.

"PV is not a climate-change solution," said Khosla Ventures Founder Vinod Khosla, who has invested both in photovoltaics and in solar-thermal startups. "It's too expensive."

In the last year, a number of large-scale solar thermal projects have sprung up, with San Francisco-based utility Pacific Gas and Electric signing a deal with Israel solar-thermal company Solel for 553 megawatts of power, and Spanish renewables producer Acciona Solar Power going live with the 64-megawatt Nevada Solar One. Projects are also underway in Spain, Morocco, Algeria and Egypt, among other places.

Proponents say concentrating solar-thermal projects like these have the potential to cut costs far lower than photovoltaic panels.

According to the U.S. Department of Energy, solar-thermal projects delivered electricity for between $0.11 and $0.18 per kilowatt-hour in 2000, compared with between $0.24 and $0.30 per kilowatt-hour for PV. Of course, solar-PV competes with retail electricity prices, while solar-thermal projects would sell at wholesale prices to utilities, so it's not an apples-to-apples comparison.

But even as he insists that solar-thermal and photovoltaics aren't competitors, van der Vleuten said the pricing hierarchy will change. "I'm very much convinced that PV is, for the long-term, the best option."

Large photovoltaic technology has the potential to drop costs 15 to 20 percent per year, and concentrating solar-thermal - despite being cheaper today - doesn't have that long-term cost-cutting potential, he said.

Photovoltaic projects are more modular, meaning the panels can be the same for a smaller project as for a larger one, and, because of this, can start out small and grow, meaning the entire project cost won't need to be fronted right in the beginning, he said.

Roberto Vigotti, chair of the IEA Renewable Working Party, said he thinks the world needs both technologies.

But he added his agreement that concentrating solar-thermal power has less room for cost-reduction. "PV one day will be delivered like a pizza," he said.

Ty Jagerson, vice president of corporate development of SolFocus, a startup with technology to use lenses to focus sunlight onto smaller solar cells for residential and commercial projects (concentrating solar PV), also was in attendance.

He said he agrees with the IEA task force that the price-cutting potential is there. At the same time, he said, "fundamentally, PV has to compete with [concentrating solar-thermal] at a basic cost point, and there's not a consensus within the industry whether PV can do that." Of course, he said he believes SolFocus' product can be price-competitive.

The task force is now looking for ways to help bring large-scale desert projects to reality.