Solar Works to Create Shift Toward ‘Clean Energy’
Process Converts Sun’s Power Into Electricity
BY ROBERT L. NOBLE
Special to the Business Journal
San Diego’s building industry soon may experience a heat wave that will revolutionize how the California sun is utilized. Photovoltaic systems, which create electricity from sunlight, are helping a growing number of buildings in the state shift from consuming energy to producing it.
Photovoltaics sometimes are confused with solar collectors, which only transfer heat to be used as an energy source. Photovoltaics, on the other hand, utilize solar cells to produce energy.
Photovoltaic cells convert solar energy into electricity at the atomic level. A typical cell consists of a semiconducting material such as a diode, which is used to create an electron current.
On top of the cell, a metallic grid or other electrical contact collects electrons from the semiconductor and transfers them to a back contact layer to complete the electrical circuit. Located above the complete cell is a glass cover or other type of transparent material to seal the cell and keep weather out. An antireflective coating keeps incoming sunlight from reflecting away from the cell. Thousands (sometimes millions) of these cells then are placed together to create a photovoltaic panel or system.
– Applications Surround Us
Photovoltaic systems already are an important part of our lives. The simplest systems power many of the small calculators and wrist watches we use every day. More complicated systems provide electricity for pumping water, powering communications equipment, heating and lighting our homes, and even running our appliances.
Photovoltaics also power nearly every satellite circling the earth, due to their ability to operate for long periods of time with virtually no maintenance. A photovoltaic system also can work effectively with an electric generator to reduce a building’s overall energy consumption.
During the daytime, photovoltaic cells serve somewhat like batteries, quietly supplying daytime energy needs. When electrical demand exceeds the capacity of the photovoltaic cells, the generator makes up the difference.
Currently, photovoltaic systems are being used or introduced as energy alternatives in a number of buildings in San Diego. Photovoltaic panels are being considered as a power source for the new San Diego Downtown Main Library, which is currently being designed for a site in East Village.
The administration building for the Environmental Services Department Operations Center in San Diego is being fitted with enough photovoltaic panels to meet 100 percent of the building’s annual power needs. As part of San Diego Gas & Electric Co.’s (SDG & E;) “Savings by Design” program, the project is expected to earn more than $14,000 in cash incentives.
As another local example, the Ocean Beach People’s Organic Foods Market is undergoing construction to be able to utilize controlled natural ventilation for cooling. A rooftop photovoltaic system will supply all of the store’s electricity during the day, and up to half of the store’s total electricity needs. Photovoltaic cells will double as shading devices by being positioned to shade skylights from direct summer sun.
Throughout California, photovoltaic arrays are being installed directly onto rooftops and mounted on freestanding structures, which are used in some cases used as carports to shade cars. In other cases, photovoltaic panels are laminated to insulation panels, or bonded to solar collectors that transfer the heat generated by the sun heating up the photovoltaic panels into the building.
Some notable installations include the Anaheim Convention Center, the Alameda County Santa Rita Jail and the Chabot Science Center in Oakland.
– Clean Energy Offers Environmental Benefits
As we become more aware of greenhouse gases and their detrimental effects on the earth, clean energy alternatives such as photovoltaic systems become more important than ever. The goal set forth by the Intergovernmental Panel on Climate Change (IPCC) is to reduce current greenhouse gas emissions by 20 percent by the year 2005. Because photovoltaic systems burn no fuel whatsoever, they could help reduce greenhouse gas emissions significantly as they are more widely adopted.
Although security has historically been a major concern for conventional power plants, especially nuclear plants, the Sept. 11 terrorist attacks have changed the way power supply security will be viewed forever. Photovoltaic power generation systems contain no explosive or toxic components which would be hazardous if sabotaged, and furthermore, these systems are smaller and more site-specific than conventional power supplies.
The disabling of a photovoltaic array would unlikely disrupt any part of the larger grid, and would be easily and safely repaired.
The cost advantages of incorporating photovoltaics into buildings have been recognized throughout the world, prompting a number of programs geared towards residential roof mounted photovoltaics.
Because photovoltaic cells use the energy from sunlight to produce electricity, the fuel essentially is free. Photovoltaic systems also have no moving parts, allowing them to operate continuously with little upkeep and minimal operating costs.
However, photovoltaics are capital-intensive, whereas most other forms of power generation have low-to-moderate capital costs, but have high ongoing costs.
– Cost Advantages Vary With System
The target cost of electricity for photovoltaic systems varies dramatically with system location, intended use, time of electricity use and the place on the grid that the electricity is supplied. For remote, off-grid systems, where the cost of electricity from other sources (such as diesel generators) is high, photovoltaics already have been demonstrated to be cost-effective.
The photovoltaic market in these areas is expanding at a rapid rate. For grid-connected systems, however, the cost advantages are not as obvious because the true cost of electricity from other sources is difficult to determine.
Because photovoltaic systems usually are placed close to where the electricity is used, they require much shorter power lines than if power is brought in from a utility grid. In addition, using photovoltaics eliminates the need for a step-down transformer from the utility line.
Less wiring means lower costs, shorter construction time, and reduced permitting paperwork , particularly in urban areas. Most photovoltaic systems also can be constructed to any size based on energy requirements and can be scaled-up easily from small to large systems. This flexibility reduces costs even further in the long run.
As energy costs continue to increase along with environmental concerns, photovoltaic systems likely will become a popular energy alternative. Rather than consuming and literally wasting energy, more buildings will be designed to help us make the most of the sunshine.
Noble is CEO and design principal of Tucker Sadler Noble Castro Architects.
