Solar-Thermal Energy Could Reduce Coal Plant’s Carbon Footprint

FEBRUARY 12, 2009

Using solar-thermal technology at coal-fired power stations could turn out to be the cheapest way to simultaneously expand solar energy use and reduce coal plants' carbon footprint. Or at least that's what the Electric Power Research Institute (EPRI) is hoping to find out with a nine-month study, Technologyreview.comreports.

The nonprofit organization recently launched a $640,000 study to understand the scale of the opportunity and the engineering challenges involved with making the two technologies work together. The study will examine the potential use of solar-thermal technology at two coal-fired power stations in New Mexico and North Carolina.

Last month, five electric utilities in the U.S. and Canada joined EPRI to host studies of the impacts of retrofitting carbon capture technology to existing coal-fired power plants.

The idea is not entirely new: about six new and existing natural-gas power stations are being designed or adapted to incorporate solar-thermal technology.  However, the overall efficiency of retrofitted hybrid solar-gas plants is still limited – when the sun goes down, a gas steam turbine that has been modified to accommodate waste heat plus solar heat will suffer an efficiency penalty from running at partial load.

However, for the hybrid technology to work, power plants will need a combination of strong sun and flat, open ground to host a solar thermal collector field. Moreover, governments need to put a firm price on carbon emissions from coal to justify trading cheap coal for more costly solar-thermal energy.

In January, EPRI noted that energy efficiency programs in the U.S. could realistically reduce the rate of growth for electricity consumption by 22 percent over the next two decades - if key barriers can be addressed.

Solar Water Heating Pays For Itself Five Times Over

ScienceDaily (Mar. 13, 2009) — An analysis of the engineering and economics for a solar water-heating system shows it to have a payback period of just two years, according to researchers in India. They report, in the International Journal of Global Energy Issues, on the success of the 1000-liter system operating at a university hostel.

The current focus in the developed world is on advanced technological approaches to alternative energy sources, such as photovoltaic cells for solar power and harnessing wind and wave with elaborate systems to generate electricity. However, the cost of such systems may be prohibitive for some applications in the developing world. They also often ignore the fact that a mundane process such as heating water might best be carried out using direct heat from the sun rather than including a waste energy-conversion step.

Vivek Khambalkar, Sharashchandra Gadge, and Dhiraj S. Karale at the Dr Panjabrao Deshmukh Agricultural University, in Maharashtra, India, explain how they have evaluated the various costs and benefits involved in solar hot-water production. They have compared solar hot-water production per liter with electrical energy approaches and found that solar heating is 57 percent of the internal rate of return.

"Solar energy is the only renewable energy source that has wide range of uses with commercial viability. Solar energy provide water heating, air heating and electricity through various modes of applications. The use of solar energy for thermal purposes is the most cost-effective way of utilizing the resource. A solar water heating system satisfies the need of warm water," the researchers explain.

Importantly, the payback time for the initial investment in equipment and installation is just two years. This compares very well to a photovoltaic system used for electricity generation if it were only being used to heat water. Photovoltaics have a payback period of several at least a decade and sometimes double that.

The solar hot water system used in the study is installed at the Jijau hostel, part of the Dr Panjabrao Deshmukh Agricultural University campus, in Akola, Maharashtra state, India. The team estimates that the system will effectively pay for itself five times over, given an estimated working life of about twenty years.

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Journal reference:

1. . Solar water cost and feasibility of solar water heating system. International Journal of Global Energy Issues, 2009, 31, 208-218

Adapted from materials provided by Inderscience Publishers, via EurekAlert!, a service of AAAS.