Small solar power plant helps freshwater producers access affordable power and heat

There are people who go from one extreme to the other. Take Utrecht-based entrepreneur Henk Arntz for example. In 2010, the former Eindhoven University of Technology (TU/e) mechanical engineering student developed a snow compressor at the university in Brabant. After graduating, he marketed his invention through the spin-off Snocom. Nowadays, a considerable number of years later, he is focusing on the complete opposite side of the spectrum with Suncom Energy. Solar power at a competitive price.

The technology used is nothing new. What is new, is the scale. Thanks to an ingenious idea by Arntz, the solar power plant can be made much smaller and cheaper. This makes it especially attractive for use in countries with abundant sunlight.

Arntz laughs briefly. “Yes, that snow compressor was really something. We developed it on the Finnish Arctic Circle and the Swiss Alps. I then sold one to Schiphol Airport. And a year later, I sold more machines to the airfields of Paris and Helsinki. Then I needed to take a break after 6 busy years.”

But now his attention is focused on his new venture, Suncom Energy. This solar power plant works on the principle of concentrating solar power (CSP). The best example of this kind of solar power plant is the Gemasolar CSP plant in southern Spain.

Bundling sunlight

“It’s actually exactly the same kind of thing little kids do with a magnifying glass. They bundle sunlight to set something on fire,” Arntz explains. The same thing happens with a CSP generator. There are four different techniques: towers, parabolas, plates and dishes. The variant I’m developing works with parabolic mirrors; long parabolic discs that are arranged in rows in the desert.”

This principle has been around for at least a century. The sunlight reflected by the mirrors heats a liquid that runs through a pipe. That could be oil, but also molten salt. The advantage offered by the latter medium is that you have a much greater efficiency from your steam turbine that you ultimately use to generate electricity.

“What’s more, the beauty of molten salt is that it is simply incredibly cheap. The storage costs are only a fraction of those for storing electricity in lithium batteries. And you also have the residual product of heat, which can be used for all sorts of process purposes. The great thing is that you only generate electricity when you actually need it. So in effect, you’ve created a thermal energy storage facility.”

Competitive with fossil fuels

According to Arntz, the cost of electricity including storage is lower than that of an array of solar panels fitted with lithium batteries. “It is also competitive with fossil fuels where electricity generation is concerned. IRENA, the International Renewable Energy Agency released a report confirming that. We are talking about facilities in sun-rich areas, such as Texas, southern Spain, Australia. In short, all sun-rich areas; and that is well over half of the world.”

However, there is one problem. In order to achieve that level of profitability, the scale of those plants must be enormous. That also entails investments of billions of dollars. Another problem is the limited grid capacity. You cannot add an infinite amount of power to the electricity grid. Solutions for this grid congestion cannot be found quickly. What’s more, the place where people need energy storage is in and around cities, not in the middle of the desert.

Two major changes

“If you have a small ‘plant’ that is close to energy users, or even on the user’s own property, then you no longer have that problem. My goal is to scale that technique down to the dimensions of a soccer field. And I basically succeeded in doing that. I made an adjustment on the receiver. That’s the pipe that you concentrate the sunlight on. That led to two major modifications of the system, which suddenly made scaling it down to profitable. Using the same specifications. I am currently developing this with my colleague Wout Gubbels, who was also involved in the Snocom spin-off from TU/e. We have now built a pilot plant in Italy to demonstrate that profitability.”

Yet scaling down is easier said than done. As the mirrors get smaller, the pipe that needs to be heated must also become thinner to achieve the same effect. “That pipe then becomes as thin as a straw. In that case, the installation costs more energy than it generates. So then the concept no longer works. However, we have found a solution to that problem using very cheap materials. This makes the small scale viable after all. I’ll be happy to explain exactly what I’ve done in about a year’s time. But not just yet!” Arntz laughs. “Because once you know it, then you think – that’s so simple!”

Freshwater producers

That said, even Arntz’s plant does have a certain natural baseline size. The minimum dimensions do depend on the equipment you end up using. The steam turbine required to generate electricity, for example, easily takes up half a soccer pitch. There are smaller turbines, but they tend to be more expensive per kilowatt. Which inevitably comes at the expense of profitability.

Suncom’s potential customers are often located on tropical islands, where in any event, electricity proces are already slightly higher. “It’s about parties that actually primarily produce freshwater. These are parties that operate in hot areas where there is not much water and who need a lot of electricity to produce freshwater, which is often very expensive there. And they also like to use heat in their processes. So I can offer both with my system.”

Payback time

“If you calculate what making an installation with solar collectors and storage in lithium batteries costs in terms of energy, the payback time is about 9 years. That’s mainly because of all the energy that you need for silicon and lithium. In the case of my setup, it takes about a year. You can extract the salt you need from nature. But that’s certainly not infinite either, which is why it’s better to use synthetic salt. It is much more environmentally friendly than just using lithium in everything. That’s much more suitable for use in mobile applications, such as transportation.”

Title photo: The parabolic mirror of the solar power plant that Arntz has developed. Photo (c) Suncom Energy.