Solar electric energy is increasingly used worldwide both in well-developed and developing countries.
The main reasons for its popularity and various uses of solar energy are:
• Free and reliable – the sun shines everyday for all of us
• Clean and renewable – unlike other sources of energy, such as coal, oil and gas, which not only are not-renewable but severely impact the global climate
• Reduces the costs you pay to your local utility company and increases your energy independence
• Can increase the value of your house – due to the lowered costs of electricity consumption
• Can be financially beneficial – if you decide to buy a PV system, you will be eligible to rebates, government incentives, feed-in tariffs, tax credits, etc.
The most common uses of solar power are related to the conversion of solar energy to electricity thanks to solar panels based on photovoltaics.
Photovoltaics transform solar energy into direct current by using semiconductor materials capable of converting solar radiation into DC voltage and current.
Solar or photovoltaic panels are used both in home and business environment. Solar panels alone however cannot generate electricity that can be practically used. Therefore solar panels together with other building blocks or components are connected together in solar electric systems.
There are two main types of photovoltaic (solar electric) systems – connected to the grid and disconnected from the grid.
Grid-tied systems allow you to offset a part of or all of your electricity demand to photovoltaics thus reducing your electricity bills.
Here is what grid-tied solar electric systems do:
• Produce electricity
• Use electricity from the grid
• Export electricity to the grid
Grid-tied systems can be designed with or without battery backup. Most of grid-tied systems are without battery backup and are usually built in regions where power outages happen rarely and for short periods.
Grid-tied systems with battery backup are preferred in areas where power outages happen more often and by users for whom electricity outage is not an option even for short periods.
Certainly you use electricity from the grid when electricity generated by your PV system does not fully cover your household electrical consumption. Moreover if your photovoltaic generator produces more electricity than you consume, the ‘excess’ of electrical energy is exported to the grid, for which you get paid.
Grid-tied systems are less expensive and require less maintenance than off-grid systems.
An obvious disadvantage is that grid-tied systems shut down in case of power outage. This can be avoided by buying a grid-tied system with a battery backup option.
Grid-tied systems are attractive because:
• Are source of significant saving from electricity bills
• Satisfy user’s own energy needs
• Add value to the building
• Protect the environment
• Provide energy backup (for grid-tied systems with power backup)
Off-grid solar electric systems are not connected to utility grid. They are preferred in areas where utility interconnection is too expensive. It should be noted that off-grid systems are more expensive than grid-tied systems. Off-grid solar systems are typically provided with battery storage.
In cases of high daily electrical consumption often a hybrid system is preferred to purely photovoltaic system since it’s not economically beneficial to offset the whole electricity to be generated by the solar system only.
A hybrid system is actually a stand-alone solar electric system with an alternative power source added – wind generator or fuel generator.
Hybrid systems are preferred in cases where too high energy consumption and/or long periods of cloudy days require a too bulky battery bank which is expensive both to buy and to maintain.
Off-grid solar systems are attractive because:
• Are a reliable source of power
• Are practically unlimited in size – a stand-alone system could serve a single device or a couple of buildings with a complex electrical network
• Can be installed almost anywhere in the world
• Can be cheaper than connecting to the utility grid (if the utility grid connection point is located miles away)
• Can provide electricity to most household devices available
Here are the main applications of off-grid solar systems
• Small solar systems for household use in developing countries
• Schools and hospitals in developing countries
• Cooling for medical or veterinary use
• Solar systems for remote homes or summer villas in well-developed countries
• Power supply for telecommunication equipment
• Water pumps in remote areas, part of portable water supply systems
• Street infrastructure equipment – street lamps, bus station dashboards, parking meters, etc.
• Recreational vehicles
• Remote meteorological stations
• Backup of important business processes, powering vending machines, electrical publicity posters, etc.
• Transportation signaling – offshore navigation buoys, lighthouses, aircraft warning light structures, and increasingly in road traffic warning signals
• Powering environmental monitoring equipment and corrosion protection systems for pipelines, well-heads, bridges, etc.
• Remote buildings, such as schools, community halls, and clinics, can benefit from solar energy.
Certainly photovoltaics can be used also for heating and cooking. This is however not beneficial, since electrical heating devices are quite ‘power hungry’, i.e. they have a high consumption. Therefore a better scenario is to use heating devices based on alternative energy resources – gas and propane.
Special attention should be paid to solar thermal systems used for water heating. Such systems are similar to photovoltaics in using the renewable solar energy. Their principle however is different – they use sun’s heat rather than sunlight.