Solar energy is a clean, renewable, and abundant source of power. with the increasing demand of sustainable energy solutions, its essential to explore ways to fully utilize solar energy. By harnessing the suns energy through advanced technologies and innovative applications, we can reduce our reliance on fossil fuels. Mitigate climate change, and create a more sustainable future.
The battery bank, not the PV array, is the main limiting factor in determining what appliances an off grid PV system can power. PV off-grid systems are ideal for low-power applications such as:
- lighting (fluorescent lamps or light-emitting diodes (LEDs), not incandescent lightbulbs)
- radios and televisions
- low-energy fans
- mobile phone charging
- laptops and low-power printers
- low-energy refrigerators
- telecom and mobile networks
- solar water pumping
- electric fencing
- small portable appliances, such as portable solar lanterns.
They can also be used for higher-power applications in different facilities:
- clinics, hospitals: lighting, refrigeration, laboratory
- schools: lighting, video
- rural businesses: low-energy power tools, office equipment
- tourism: remote lodges, game parks, solar boats
- veterinary applications: fridges for animal vaccines
- back-up systems (PV generally only suitable when power outages are frequent and last more than a few hours)
- mini-grids (direct current (DC)-coupled and alternating current (AC)-coupled)
The following appliances are usually not suitable for off-grid systems because they consume too much power: cookers, water heaters, electric heaters, electric kettles (any appliance that generates heat), air-conditioning units, large halogen security lights (500 W), etc. In most cases, however, non-electric alternatives are available. Essential heavy loads in hospitals, such as x-ray machines (~10 kilowatts (kW)) or sterilizers, are usually powered by diesel generators.
Should DC or AC appliances be used? DC appliances need to be used in DC-only systems, and the range of DC appliances now available (especially for lighting) is extensive. DC appliances are generally more energy-efficient than AC appliances – they need to be, since they are designed to run on batteries. AC appliances are more widely available and usually cost less than DC appliances. Decisions need to be made on a case-by-case basis. However, if you want to power AC appliances with an off-grid PV system, you need an inverter.
Application example: solar water pumping.
In many parts of the world, the main source of water is groundwater reserves. Wells are drilled to access the water, which is pumped to the surface for distribution and use. Running the pumps can be costly and unreliable, especially in remote rural areas with no access to grid-based electricity. Water demand is often highest when solar radiation levels are high, which makes PV an ideal power source to drive the pumps.
Solar water pumping is a very successful branch of the solar industry, or, one could say, a very successful branch of the water pumping industry. Over a million solar pumps are already in use worldwide. In many areas, they are replacing hand pumps, mechanical and electrical diesel pumps, and even grid electricity.
Some general points on solar water pumping:
- It is generally more suitable for water supply for humans and animals than crop irrigation (except for small-scale systems and at low heads, i.e. where the well is not too deep).
- Solar water pumps usually do not include batteries – water is pumped when the sun shines and is stored in a tank at or above ground level.
- At low heads, it can be particularly cost-effective.
- Deep-well pumping can be expensive, with the borehole costing more than the PV system.
Solar water pumping system schematic( Source: Solar Magazine Uganda.)
Application example: Telecommunications.
• describe the potential application of PV off-grid systems in the telecom industry
A vast potential market for off-grid PV is the telecom industry—specifically, powering the base stations for telecom/mobile phone networks in remote areas without access to the electricity grid. Power demand ranges from a few hundred watts peak (Wp) to several thousand Wp. DC power is required for the retransmitting equipment. AC power may also be required for ancillary equipment (air conditioning, lighting, fire alarms, etc.). The design, sizing, component selection, and installation of these systems is a specialized branch of the industry. Many low- and middle-income countries have in recent years seen a significant increase in the number of mobile towers in areas with either no or unreliable grid connection. Most of these are still powered by diesel gensets, but the potential for powering these from off-grid PV is great. For more information, see GSMA Green Power for Mobile:
Off grid PV powered telecom system with backup diesel generator .(Source: solar magazine Uganda)
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