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Guide: How solar energy works

Hybrid solar system diagram.

Kenyans use the Internet to know what solar energy is. Questions people are typing show a lot is unknown about solar energy. Where does solar energy come from? How does solar energy work? Is solar energy reliable? Can solar energy be used for cooking? Can solar energy run a refrigerator? Can solar energy be used at night?

We talked to two solar energy experts to introduce us to solar energy. Mr Aidarus Abubakar, managing director, Solargen Technologies Limited, and Ms Agnes Mwangi, senior technical sales executive, Techwin Limited.

Energy and Petroleum Regulatory Authority has licensed Mr Abubakar and Ms Mwangi as solar technicians, contractors, and sellers.

Solar power is the electricity generated using the sunlight from the Sun. Solar panels use energy from the Sun to generate electricity. Solar panels are also known as photovoltaic (PV) systems.

Solar panels have cells which turn chemical energy to electronic energy. There are two types of electrical energy, alternating current (AC) and direct current (DC). Alternating current flows back and forth alternating directions. Direct current flows consistently in the same direction.

The electricity produced from a solar panel is direct current. Solar battery keeps this solar energy as direct current.

But consumers must change this direct current energy to alternating current to use it at home or office for lighting and electric appliances. Most of home appliances work on alternating current. In Kenya consumers are connected to Kenya Power, which supplies alternating current.

Solar energy uses the same wiring as electricity supplied by Kenya Power.

“When installing a solar system, a consumer does not need to have a separate wiring if their house or building already has wiring for Kenya Power,” Ms Mwangi said.

Parts of solar energy

Solar panel – Solar panels collect energy from the Sun and convert it into electricity that can be used to power homes or businesses. When installing a solar panel, you must choose proper angle to get more sunlight. A solar panel will harness the most power when the Sun’s rays hit its surface vertically. Ensuring that solar panels face the correct direction ensures they (panels) produce maximum energy.

Charge controllers – Solar controllers adjusts the flow of electricity from solar panels to batteries. Usually, the charge controller is placed between the solar panels and the solar battery. But in case of a solar powered borehole, the charge controller is placed between the solar panel and water pump. The charge controller gives a battery or a pump the right amount of power, Mr Abubakar said.

Solar battery – Solar battery stores excess solar energy from the solar panels for later use. Thus, it ensures continuous electricity even when there is no sunlight. The surplus power generated by the solar panels is used to charge the batteries.

Solar inverter – Solar inverter converts direct current coming from solar battery into alternating current. This makes it possible for standard electrical equipment to use the energy. To use power from the battery it must go through an inverter to change it from direct current to alternating current. You don’t need an inverter if you are using a borehole.

Can all electrical machines use solar energy?

Ms Mwangi says there is no item solar energy cannot work with. But regulations ban use of solar energy to run escalators or lifts.

“Devices with motor, for example fridge and iron box, use a lot of power to start,” she said. “But if all power consumption is calculated and adequate [solar] system is installed all appliances will run on solar energy.”

The important thing to always ensure is to match power demand with power supply, Ms Mwangi said.

There are two main types of solar water heaters. Flat plate (left) and pressurised heat pipes (right).
There are two main types of solar water heaters. Plate (left) and tube (right).

You must separate solar water heating

The solar professionals advise consumers to have a solar water heating system that is separate from solar home system. The solar home system is for lighting and powering appliances while solar water heater is for heating water for kitchen and bathroom.

Ms Mwangi said there is no way to heat water using solar power energy due to high power demand of the heater. In solar water heating system, water is heated directly and supplied to the house.

“You must have separate solar water heating and solar lighting,” she said.

Mr Abubakar advised consumers to use a solar water heater for heating water for use in the kitchen or for bathing. “It’s cheaper to run a water heater on solar than using an instant solar water heater powered by the grid [Kenya Power],” he said.

A solar water heater is installed on the roof. It consists of collectors facing the sun to absorb sunlight. Cold water enters the vacuum collector tube, where it is heated by the solar energy absorbed by the collector. The heated water rises and enters an insulated tank. The insulated tank prevents water from losing heat for about 12 hours.

There are two main types of solar water heaters, the tube and plate. The tube uses glass tubes to absorb sunlight. The plate is an insulated rectangular box covered by glass.

Mr Abubakar said flat plate solar water heater is unsuitable for heating salty water.

What size of solar water heater does a family need?  “A 300-litre solar water heater system is enough for a typical size of family to get enough warm water for bathroom and kitchen use,” he said.

Things you must know about solar energy

Stability of the installation. Ms Mwangi said the roof to hold solar panels must be strong to withstand 500 kilogrammes. “When constructing you should build a strong roof if you are planning to have solar energy,” she said. “So, you don’t have to reinforce your roof later.”

Direction of solar panels. Ensuring solar panels face the correct direction exposes them to high intensity of sunlight thus producing maximum energy. In Kenya, Ms Mwangi said panels must be placed North-South to capture maximum sunlight as the Earth moves from West to East.

Obstruction. Are there trees around? Your roof should be free from shadows and obstacles, for example, trees. Anything blocking the sunlight will make your solar panels less efficient.

Installation warranty. After installation the technician doing the work must give the customer a workmanship warranty for their service. Ms Mwangi said the workmanship warranty depends on the system, but it ranges between six and 12 months.

Products warranty. A customer must get warranty for each product they buy, said Ms Mwangi.

How consumers can avoid failure when installing solar energy

  1. Most pitfalls can be avoided by using installers or technicians who hold licence from Energy and Petroleum Regulatory Authority, Mr Abubakar said.
  2. Solar equipment manufacturers offer product or quality guarantees or warranty. The warranty shows the lifetime of the equipment, Mr Abubakar said. For example, for two types of inverters, one could be more expensive than the other. But the expensive one might have a longer warranty. “If a manufacturer is willing to give you a longer warranty it means they have faith in the quality of their product, he said.
  3. Good solar equipment is expensive, and if it is unsafely installed, the warranty is “For instance, one lead acid battery costs around Sh30,000,” Mr Abubakar said. “It’s a big loss if it’s damaged because of poor installation carried out by uncertified technician.”
  4. Ensure you get equipment from approved distributors. It is important to obtain quality products however high the price is, Mr Abubakar said. He gave the example of a solar battery. The quality of a battery is measured by how much of its capacity can be used in a day and how many times it can be charged and recharged. Low quality batteries give less than 1,000 cycles, that is, the number of times you can charge and recharge. So, 1,000 divided by 365 days means the battery will last for 2.7 years.
  5. “The ultimate safeguard is to consult professionals so they can advise on the available technologies and choice of equipment under specific operating conditions,” Mr Abubakar said.

He said people avoid using solar energy because of the cost at the beginning.

“But when you critically look at the cost in the longer term, it’s inexpensive,” Mr Abubakar said. “As such, consumers should consider the lifetime cost of the solar.”

About Kaburu Mugambi

Kaburu Mugambi is a veteran of business reporting having worked with two national newspapers in Kenya. He is a graduate of economics from Kenyatta University. He started his journalism career in 2000 with The People Daily as a business reporter before becoming a business sub-editor. He joined Daily Nation in 2004 as a business writer. He holds a post-graduate diploma in mass communication from University of Nairobi's School of Journalism and an MBA in marketing from the same university. In 2016, he founded Water Tower, a media firm focused on water, energy and climate. Its content cuts across water, energy and climate with emphasis on adaptation and sustainability.

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