What are Solar Farms?
While homeowners with solar panels on their roofs aim to generate enough power to cover their individual energy needs, large utility-scale solar farms are designed to generate enough electricity to power thousands of homes and businesses. Who do solar farms work? A solar panel farm feeds power into the electrical grid just as fossil-fuel energy plants do, except that solar farms produce no pollution of any kind, and use very little water compared to traditional power plants.
Photovoltaic (PV) cells made of silicon are constructed into panels, each gathering a small amount of sunlight energy. The panels are installed on short towers over an area as big as 100 acres. Some solar farms fix their PV panels into a static position; other farms use solar tracking systems that move the panels to follow the sun. Multiple panels are required to generate significant electricity, which is why solar panel farm arrays are so large. Solar developers either buy the land for their panels, or lease it from businesses, government agencies or private individuals.
Another form of solar farming energy is concentrated solar power, which uses mirrors or lenses to concentrate sunlight and create heat, which drives a variety of conventional generator systems. PV solar farms are more popular and in much greater use, outnumbering concentrated solar power installations by 40 to one.
Solar farms produce no pollution of any kind, and use very little water compared to traditional power plants.
Most of the existing utility-scale solar panel farms are owned and operated by independent power producers, but the number of projects owned by communities and utilities is increasing. Developers of solar farms have benefitted from the solar investment tax credit (ITC), which reduces the federal tax liability for individuals or businesses that purchase qualifying solar energy technologies. In December 2015, Congress extended tax and production credits for renewable energy for five years, which is expected to significantly expand renewable energy projects in the United States, including solar panel farms.
With current PV technology, solar farming developers need approximately 2.5 acres of solar panels in high intensity sun areas to produce a megawatt of electricity; in moderate sun locations, about five acres of panels are needed to produce a megawatt. A megawatt is one million watts, and enough energy to power 650 residential homes for one day.
California is the number one solar farming state in America, producing enough solar energy to power well over one million homes. In the next tier of solar states is North Carolina, Nevada, Massachusetts, Arizona and New Jersey, with enough capacity to power between 38,000 and 50,000 homes. Third tier states New York, Texas, Hawaii and New Mexico generate enough solar energy to power between 14,000 and 25,000 homes.
In the twelve months through October 2015, utility scale solar power generated 25.8 terawatt hours (a terawatt is a trillion watts), which was 0.63% of total U.S. electricity. In 2015, one third of all new energy generation in the United States was solar power. There are so many solar farms under production in the United States right now that existing capacity is expected to double by 2017.
The following are the important key factors to be considered before setting up a solar captive power plant:
1. Load Supported
They are usually the largest single influence on the size and cost of a PV system. A PV system designer can minimize a PV system’s cost by efficiently using the energy available. The first step is to estimate the average daily power demand of each load to be use. It is important to note that one should be thorough, but realistic, when estimating the load. A 25 percent safety factor can cost a great deal of money.
2. Type of Loads
While estimating the load, it is necessary to calculate for both ac and dc loads.
3. Hours of Operation
An hour of operation is an important factor. This value helps us determine the exact consumption of electricity (kWh) of each appliance. Calculating this value will help the designer in the first level assessment of the size of the solar system that will be needed to power the site under consideration. More importantly the time of operation during the day will enable a designer to do a more accurate sizing of the PV system. For example, a refrigerator runs for 24 hours in a day. Other appliances like washing machine will run 2 hours a day in the afternoon. So a PV system can be designed to supplement grid electricity by providing electricity during peak hours. It is also possible, if the user wishes, to design a complete solar system to provide electricity throughout the day with battery backup.
4. Days of Autonomy
Autonomy refers to the number of days a battery system will provide a given load without being recharged by the PV array or another source. General weather conditions determine the number of “no sun” days which is a significant variable in determining the autonomy. Local weather patterns and microclimates must also be considered. Cross-check weather sources because errors in solar resource estimates can cause disappointing system performance.
The most important factors in determining an appropriate autonomy for a system are the size and type of loads that the system services. The general range of autonomy is as follows.
2-3 days for non-essential uses or systems with a generator back up
5-7 days for critical loads with no other power source
5. Space Available
For setting up 1 kW SPV system without batteries, the required shade free area is 100 sqft.
Knowing the installation site before designing the system is recommended for good planning of component placement, wire runs, shading, and terrain peculiarities. The primary requirement in selecting the space is that, it should be shade free. Shading critically affects a PC array’s performance. Even a small amount of shade on a PV panel can reduce its performance significantly. For this reason, minimizing shading is much more important in PV system design. Carefully determining solar access or shade-free location is fundamental to cost effective PV performance. . When a site is selected, be sure that the following parameters are met and tasks completed.
Be sure that the array is not shaded from 9 A.M to 3 P.M.
Identify the obstacles, if any, that shade the array between 9 A.M and 3 P.M
Make recommendations to eliminate any shading, move the array to avoid shading, or increase the array size to offset losses due to shading.
Other factors to be considered
Keep it simple – Complexity lowers reliability and increases maintenance cost.
Understand system availability – Achieving 99+ percent availability with any energy system is expensive.
Know what hardware is available at what cost – Tradeoffs are inevitable. The more you know about hardware, the better decisions you can make. Shop for bargains, talk to dealers, ask questions.
Install the system carefully – Make each connection as if it had to last 30 years– it does. Use the right tools and technique. The system reliability is no higher than its weakest connection.
Safety first and last – Don’t take shortcuts that might endanger life or property.
Comply with local and national building and electrical codes.
Plan periodic maintenance – PV systems have an enviable record for unattended operation, but no system works forever without some care.
Calculate the life-cycle cost (LCC) to compare PV systems to alternatives – LCC reflects the complete cost of owning and operating any energy system.
Know Whether Rooftop Solar Generates Power During Power Failure
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