Renewable Energy is  collected from renewable sources, which are naturally replenished on a human timescale such as sunlight, wind, water and rain, tides, waves, and geothermal heat. Kenya has utilized four of these sources; but there is much potential for tides and waves. This is because it neighbors the Indian Ocean through its Coast region. Ocean bodies can produce two types of energy: Thermal Energy from the sun’s heat, and Mechanical Energy from the tides and waves due to gravitational forces exerted by the moon and the sun and the rotation of the earth.

The relative motion of the Sun, Moon and the Earth produces different tidal cycles which affect the range of the tides. In addition, the tidal range is increased substantially by local effects such as shelving, funneling, reflection and resonance. Energy can be extracted from tides by creating a reservoir or basin behind a barrage and then passing tidal waters through turbines in the barrage to generate electricity.

Ocean Thermal Energy Conversion (OTEC) is a process that can produce electricity by using the temperature difference between deep cold ocean water and warm tropical surface waters. OTEC plants pump large quantities of deep cold seawater and surface seawater to run a power cycle and produce electricity. As long as the temperature between the warm surface water and the cold deep water differs by about 20°C (36°F), an OTEC system can produce a significant amount of power.

The technology required to convert tidal energy to electricity is numerous but one that is well documented is the Tidal Barrage. It is a dam-like structure used to capture the energy from masses of water moving in and out of a bay or river due to tidal forces. Instead of obstructing water on one side like a conventional dam, a tidal barrage first allows water to flow into a bay or river during high tide, and releasing the water back during low tide.

It works similarly on a hydroelectric scheme, except that the dam is much bigger and spans a river inlet. When the tide goes in and out, the water flows through tunnels in the barrage. The receding tide and flow of the tides can be used to turn a turbine, or it can be used to push air through a pipe, which then turns a turbine  then generates electricity.

Technologies of producing Marine Energy

Wave Power System converts the motion of the waves into usable Mechanical Energy, which in lumpsome can be used to generate electricity. Wave power converts the periodic up-and-down movement of the oceans waves into electricity by placing equipment on the surface of the oceans that captures the energy produced by the wave movement and converts this mechanical energy into electrical power.

Float Or Buoy Systems uses upward and downward motion of waves, combined with the weight of a metal plate, to move a hydraulic piston, resulting in electricity. The Plate can be mounted to a floating raft or to a device fixed on the ocean bed. Between the surface buoy and the metal plate is a large hydraulic cylinder with a piston inside. As the buoy rises and falls, it pushes and pulls on this piston. This forces hydraulic fluid through a hydraulic motor, which in turn runs an electrical generator to produce electricity.

Oscillating Water Column (OWC) devices applies the in-and-out motion of waves at the shore where they enter in a column and force air to turn a turbine. The enhanced design reduces turbulence at the entry to the OWC and drag inside the chamber, resulting in considerable increase in capturing wave power and system efficiency.

Tapered Channel rely on a shore-mounted structure to channel and concentrate the waves driving them into an elevated reservoir. Water flow out of this reservoir is used to generate electricity using standard hydropower technologies.

Finally the Ocean Thermal Energy Conversion (OTEC) system seeks to turn the solar energy trapped by the ocean into useable energy. OTEC systems use the ocean’s natural thermal gradient. The fact that the ocean’s layers of water have different temperatures to drive a power-producing cycle. As long as the temperature between the warm surface water and the cold deep water differs by about 20°C (36°F), an OTEC system can produce a significant amount of power.

Policy formulation

Although the assessment outcome points out that Mombasa and Lamu tides and tidal energy sources are viable for exploitation. There has been noted challenges including: high capital costs, political instability, annual reliable energy density, technology level upgrade and human capacity competence. There is need for formulation of necessary policies and networks to realize the overall ocean energy potential and promotion.

By Gabriel Kihara,NETFUND


National Water Conservation and Pipeline Corporation 1st Floor, Dunga Rd, Nairobi, Kenya

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