Building a Viable Solar Sector

 

TODAY, SOLAR PHOTOVOLTAIC ELECTRICITY is widely recognized as an energy source fueled not only by the sun, but also by incentives and renewable portfolio mandates. If PV is to become a significant part of the global energy portfolio, the cost per watt must continue to fall.

There are two ways to lower the cost-per-watt: increase conversion efficiency and lower manufacturing cost. These can be accomplished simultaneously. Furthermore, history shows us how powerful economies of scale can be. In the last two years, the price of monocrystal-line silicon-based panels fell by more than 30 percent as new capacity has come on line.

Increasing efficiency is a leveraging option. With higher efficiency, a given manufacturing line has greater capacity. Fewer modules are needed to produce an installation with a given power output, lowering the balance of system cost. Also, offering higher power modules can give a manufacturer a differentiated product in a crowded market.

New techniques to raise efficiency that add manufacturing steps must be accompanied by improved manufacturing processes to offset the extra complexity. Double-printed contact lines, to take an example from crystalline silicon PV, can add 0.5 percent absolute efficiency, but implementing this technique requires more screen printers, which could raise both capital and operating expenditures.

So, how can manufacturing cost increases be offset? In this case, sophisticated machine vision and process control systems allow the consumption of the silver screen printing paste to be reduced while more light enters the cell. The advanced statistical process control ensures that a tighter distribution of higher power cells is produced.

In thin-film silicon PV, texturing the front-side contact of the cell can raise the relative efficiency by 10 percent. However, the manufacturer can no longer buy off-the-shelf transparent conductive oxide glass, but must add wet etch processes to the line.

Here, nanotechnology offers opportunities to offset the extra complexity by increasing the efficiency of material use. Advances in thin film deposition technologies have allowed us to deposit films using less gaseous raw materials, which reduces the net materials cost of the completed solar module. Similarly, advances in deposition rates and film patterning techniques allow precise control of film thicknesses and device geometry over large areas at high speed, thereby delivering a combination of lower costs through higher tool productivity and higher coated-area utilization.

The same advances in thin film deposition can reduce system installation costs. By achieving precise material control over large areas, we can make production of large-area solar modules, which are less expensive to install at a utility scale, cost-effective. For example, 5.7-square-meter solar modules – about four to eight times the size of traditional solar modules – are ideally suited for ground-mount installations and enable considerable reductions in installation complexity, time and labor costs. You might say that nanotechnology enables mega-modules for megawatt solar projects.

Reliability and warrantability are key concerns when implementing any new power-generating technology. The latest high-efficiency modules, both thin film and crystalline silicon, provide stable, predictable power generation over the 25 years or longer of environmental stresses that the modules will experience. By protecting the critical energy-conversion materials of a solar module, the overall durability and lifetime are increased, with attendant reductions in cost per kilowatt-hour.

The potential of factory automation software to increase the efficiency of manufacturing operations should not be underestimated. In the semiconductor industry, automation software is pervasive, offering complete control over manufacturing from a single chip all the way to multi-factory enterprises. Advanced techniques such as predictive scheduling, closed-loop process control and automated fault detection and classification can produce enormous increases in factory output without additional capital equipment, leading directly to reduced cost-per-watt at the module level.

Finally, as more attention has been devoted to PV technology, the industry has come to understand that solar PV is a manufactured source of energy. Until a few years ago, solar PV was a boutique industry characterized by low volumes, high costs and custom designs and installations. Since then, new advanced manufacturing techniques are creating the solar factories of the future, which are necessary for scaling, just like we saw with the semiconductor and display industries.