Prof. Avi Kribus of Tel Aviv University’s School of Mechanical Engineering and its innovative new Renewable Energy Center is applying the term “hybrid” to power plants (More info)
Prof. Kribus has developed a new technology that combines the use of conventional fuel with the lower pressures and temperatures of steam produced by solar thermal power, allowing plants to be hybrid, replacing 25 to 50 percent of their fuel use with green energy.
The professor explains most power plants create power by using fuel. Solar thermal power plants use high temperatures and pressures generated by sunlight to produce turbine movement are currently the industry’s environmentally friendly alternative. But it’s an expensive option, especially when it comes to equipment made from expensive metals and the solar high-accuracy concentrator technology used to harvest solar energy.
In a solar thermal power plant, sunlight is harvested to create hot high-pressure steam, approximately 400 to 500 degrees centigrade. This solar-produced steam is then used to rotate the turbines that generate electricity.
Prof. Kribus cautions that it is somewhat unrealistic economically for the power industry. “It’s complex solar technology,” he explains. The materials alone, which include pipes made from expensive metals designed to handle high pressures and temperatures, as well as fields of large mirrors needed to harvest and concentrate enough light, make the venture too costly to be widely implemented.
With his graduate student Maya Livshits, Prof. Kribus is developing an alternative technology, called a steam-injection gas turbine. “We combine a gas turbine, which works on hot air and not steam, and inject the solar-produced steam into the process,” he explains. “We still need to burn fuel to heat the air, but we add steam from low-temperature solar energy, approximately 200 degrees centigrade.” This hybrid cycle is not only highly efficient in terms of energy production, but the lowered pressure and heat requirements allow the solar part of the technology to use more cost-effective materials, such as common metals and low-cost solar collectors.
Kribus and Livshits’ method presents a potentially cost-effective and realistic way to integrate solar technology into today’s power plants is to be published in a future issue of the Solar Energy Journal.
Its not a totally alternative solution, but substituting a quarter to half of the fuel with solar is no small thing. A hybrid plant does offer a more realistic option for the coming decades.
Krivbus points out electricity from solar thermal power plants currently costs about twice as much as electricity from traditional power plants. If this doesn’t change, solar technology may never be widely adopted. Kribus and Livshits’ hope that a hybrid plant will have a comparable cost to a fuel-based power plant, making the option of replacing a large fraction of fuel with solar energy more competitive and practical.
The news story offered at the university site doesn’t address the peak load issues, nor the impact on a plant’s productivity after sundown. But from the point of view in the Middle East where air conditioning is a major part of power use, the harvest of solar during the day’s heating period should make great sense.
Kribus and Livshits are starting a collaboration with a university in India to develop the design in more detail, and are looking for corporate partnerships that are willing to put hybrid technology into trial use. Kribus knows it’s a stepping-stone that will help introduce solar energy into the industry in an accessible and affordable way.
This is quite an innovative approach. We’ll be keeping an eye out for how the application of Indian engineering and more minds up close can improve the basic concept. The first impression on the physics seem good, now if they can just keep the power level up into night . . .
By. Brian Westenhaus