Harnessing the Solar Energy with a promising Concentrating Photovoltaic (CPV) system
The concept of concentrating the sun’s energy has been around since ancient Greece when some historians believe that Archimedes used mirrors and the sun’s energy to set attacking Roman ships on fire. Frankly, some people think concentrator technology hasn’t come very far since then. However, concentrating photovoltaics (CPV) has advanced considerably in the last few decades—not to mention the last handful of years.
Solar energy has got a major pie of renewable energy and we can’t ignore during in any energy planning due to its availability around the globe. It’s a sustainable energy source which environment has given to us.
The traditional PV system till now has been the main source for harvesting solar energy. A promising Concentrating Photovoltaic (CPV) system could lead the future due to its higher efficiency and energy conversion rate.
This Amonix system consists of thousands of small lenses, each focusing sunlight to ~500X higher intensity onto a tiny, high-efficiency multi-junction solar cell. A Tesla Roadster is parked beneath for scale. (Image source: Wikipedia)
Traditional photovoltaic (PV) modules use semiconductors to generate electrical power by converting solar radiation into electricity. PV modules come in many forms, including crystalline silicon modules and thin-film modules based upon amorphous silicon, cadmium telluride, and copper indium gallium selenide. Typically, polycrystalline silicon modules have efficiencies of ~14-15 percent, while thin-film modules have efficiencies of ~8-13 percent, depending upon the technology.
For those new to the topic, a concentrated solar PV (CPV, for concentrated photovoltaic) refers to a system in which a large array of reflecting surfaces focuses the sun’s rays on a smaller array of solar cells. That’s not to be confused with concentrating solar power technology, in which heliostats (that’s fancy speak for special mirrors) or trough-shaped structures focus solar energy to heat a liquid, which is then used to generate steam for a turbine.
A Concentrating Photovoltaic (CPV) system converts light energy into electrical energy in the same way that conventional photovoltaic technology does, but uses an advanced optical system to focus a large area of sunlight onto each cell for maximum efficiency. Different CPV designs exist, sometimes differentiated by the concentration factor, such as low-concentration (LCPV) and high concentration (HCPV).
Yearly Installed CPV Capacity in MW from 2002 to 2013 (Image source: Wikipedia)
The other primary difference is in the cells. Traditional PV systems utilize large-area silicon solar cells. In contrast, CPV systems utilize small-sized high‐efficiency solar cells, thus consuming much less semiconductor material. Cells used in high concentration CPV systems are typically multi-junction solar cells made out of compound III‐V semiconductor materials. Low concentration CPV systems typically use small-sized high-efficiency Silicon solar cells. The CPV panels are mounted on a tracker which follows the sun. For high-concentration systems, two-axis tracking is mandatory, for low concentration systems sometimes one-axis tracking is sufficient.
CPV is sometimes confused with CSP – Concentrating Solar Power. Whereas PV converts light energy directly to electricity, CSP systems utilize heat from the system to generate power in a traditional steam engine power plant environment.
CPV provides the lowest cost of solar energy in high solar regions of the world. The technology is in its early stage with significant headroom for future innovation, and it has the ability to ramp to gigawatts of production very rapidly. Many of the limitations for PV in the past are overcome by advances in CPV technology.
Challenges for CPV
One important technical challenge for CPV is reliability. As with flat-plate PV and wind energy, CPV needs to be reliable so that utilities will trust the technology and buy into it. One of the key ways to ensure reliability is to develop codes and standards that CPV technology must reach to be certified. Perhaps the biggest challenge facing the CPV industry has less to do with technological hurdles than with developing a market.
The cost of CPV manufacturing cost also needs to be reduced so that it can be available to a major part of the world. The manufacturers of CPV systems have got tough competition from its counterpart – the conventional PV system manufacturers as far as cost, market penetration, accessibility, and acceptability by the end-users.
Going forward
There is currently a great deal of effort aimed at the commercialization of these concentrating PV (CPV) systems. The current paradigm, however, relies on large-scale assemblies of Fresnel lenses or mirrors that must be pointed toward the Sun throughout the day to concentrate its light. Although this approach is well-suited for large, open-land areas, it is incompatible with the limited space and compact panel profile required for rooftop installation.
Concentrating PV offers many benefits over other ways of producing electricity, but, like wind energy in its early days, it also faces many challenges. Although research on cells, modules, and systems for CPV has been ongoing for decades, CPV only entered the market in the mid-2000s. While it has seen strong market growth in recent years, it is still a young and – compared to conventional flat-plate PV – a small player in the market for solar electricity generation.
