Solar trackers, devices that rotate solar panels or thermal collectors to follow the sun across the sky, are getting renewed interest from global solar firms. The obvious reason being a significant improvement in power output. Solar tracker manufacturers boast a 30-40% increase in electricity production compared to fixed models.
Considering only such significant production increases, it is hard to fathom why the majority of today’s solar arrays — both residential and commercial — do not utilize tracking technology. That answer lies in economic controversy. The issue lies in increased production versus cost of implementation. In other words, if the cost of installing and maintaining the tracker (which usually introduces moving parts into the solar equation) outstrips the value of the increased energy output, then economically it is a losing cause.
That appears to be changing these days, at least on the industrial and commercial levels, as new tracker technology advances. Residential applications are still barred by cost and the usual location of the systems — on rooftops — which often minimizes the effectiveness of a tracking system. Solar tracking systems for all markets are best suited for ground mount systems.
There are two types of active, or driven, solar trackers; as well as one passive breed.
Active solar trackers are single-axis or dual-axis models. Single-axis are designed to move azimuthally (horizontally) from east to west over the course of the day and then reset in time for morning. Dual-axis trackers rotate both horizontally and vertically to adjust for both the sun’s movement across the sky and its height as seasons change.
Active trackers use gear trains, motors, or hydraulics to run the trackers. Passive solar trackers, while serving the same essential function, use a compressed fluid with a low boiling point to move the system. Passive systems avoid much of the potential maintenance requirements and energy usage inherent to motorized trackers but are less accurate at tracking the sun.
The percentages (of increased output) vary by the latitude of a given array, but the average increase in production induced by a single-axis between 27-32% compared to fixed panels while a dual-axis system can increase that to 35-40%. Percentages such as these are a big reason why solar trackers are catching on so fast in the commercial sector, where economies of scale help stem costs while increasing return on investment.
According to Renewable Energy World, the solar tracker segment of the global solar industry is poised to take off. In fact the signs are already there, especially in places like Spain, and greater Europe as well, which has enjoyed a major boom in large-scale solar production over the last few years thanks to aggressive government incentives for concentrated solar power.
Indeed it is the need for maximum precision in concentrated solar power (CSP) plants that is driving the emerging tracker market at this time. With much of the global attention and production in Europe, SunPower is making the biggest impact in the United States. Based in California, SunPower is one of the world’s largest single-axis solar tracker manufacturers. And they’ve enjoyed some very significant deal-signings in the first half of 2009.
Among these are several individual deals with FPL Group in Florida, one of the nation’s largest renewable energy developing utilities. Those deals include both a supply agreement for SunPower Trackers over the next few years and several PV power plants using SunPower trackers and modules.
Meanwhile in Chicago, SunPower is part of a joint project to develop the nation’s largest urban solar tracking PV plant on a brownfield on Chicago’s South Side; a plant that will eventually comprise 32,800 solar modules. Other SunPower solar tracking projects include a plant in Australia and their sizable agreement with Nellis Air Force Base in Nevada.
Tracks of Land
If there is a downside to utility-scale solar tracking power plants it is land-use. Because the modules are tracking (and often one commercial solar tracker will house dozens of solar modules), they must be prevented from shading one another as they navigate the sun’s path across the sky. This means that panels must be spaced farther apart, thus wasting space and increasing land costs for the developer.
Again, everything comes down to cost versus revenue. If the increased revenue from more production can outweigh the higher cost of more land or the hit taken by less energy-making modules, then most companies will gladly invest in the trackers. And based on recent activity within the solar tracker market, I’d say that for many solar firms — who are backed by government incentives as well as capital — the financial numbers are truly on track.