Power Engineers are justly concerned by the problems of integrating renewable resources in power networks designed to operate with conventional generating plants. In this country the problems of large-scale integrations of renewables to our aging or a modernized national grid has not attracted any attention it deserves, mainly because it is unlikely to be faced in the 10 – 15 years from now. What are the likely challenges of a future Smart National grid with such massive integration of renewables?
My fellow Power engineers will agree with me that power systems are designed to cope with substantial variability of demand. If a variable source is added in small amounts, there will be negligible consequences since its variability will be swamped by that of the demand.
A number of studies have shown that supplying upto 20% of the demand from renewable sources will require no modification in the way the systems are run at present.
For larger penetrations, the energy from renewable sources will become increasingly less valuable unless appropriate policies are implemented to co-ordinate the output from a variety of renewables.
The penalties to be paid if the penetration from say, wind and tidal (if in future is exploited on the Kenya Coast) will be substantial due to the following:
• Cycling losses due to increased start-up and shut-down of thermal plants.
• Reserve costs arising from the need to ensure that the system can respond adequately to unpredicted changes.
• Discarded energy when the available variable input exceeds the amount of which can be safely be absorbed while maintaining adequate reserve and dynamic control of the system.
Variable power sources – solar, wind, tidal are all characterized by high costs and very low operating costs hence it is possible to make them base plants per excellence i.e. their output could be accepted whenever it is available. Note that solar and wind are intermittent resources which require additional resources for stabilization.
In the power system of the future containing supposedly all the three types of plants, with gradual phasing out of capacity-limited plants, the policy in my view should be to maximize the use of renewables with energy-limited plants supporting variable power sources and capacity-limited plant used as little as possible.
The hydrogen generated from the renewables can be used to power the remaining capacity –limited plants and also provide portable fuel for transport and industrial use in future.