Thu | May 25, 2017

Why Jamaica needs flexible electricity generation

Published:Sunday | May 10, 2015 | 5:00 AM
Member of Parliament Delroy Chuck (right) displays the SolarMill, a hybrid renewable energy system that harnesses the energy of the sun and wind on the roof of his law office in downtown Kingston, to Phillip Paulwell (centre), minister of science, technology, energy and mining, and Kelly Tomlin (left), CEO and president of the Jamaica Public Service Company.
Two students look at a wind turbine operating at the Wigton Windfarm in St Elizabeth.
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In 2016, electricity generated from renewable resources (generating units) in Jamaica will potentially double in net energy output to the grid.

Despite this significant increase, this represents just 10 per cent of all Jamaica's energy when the Government's target is to have 30 per cent of all power generated from renewable sources. The expectation is that electricity prices should gradually get cheaper when fossil fuels are replaced by renewable energy.

However, significantly increasing the penetration of intermittent renewable resources such as wind and solar without a proper grid-management plan can introduce system instability.

This means that existing fossil fuel plants need to be flexible in how they operate when these renewable systems are in service. They must be able to start and stop quickly; ramp up (increase output) and ramp down (reduce output) quickly; and not increase operating costs for these start, stops, or ramping up and down.

Integrating intermittent

renewables

For example, when the 20 megawatt (MW) solar farm planned for Clarendon is operating under a blue sky at noon, other plants in the system should ramp down. That's because if renewable energy is not used immediately when it is generated, it will be lost if there is no storage (e.g. battery) devices on the renewable plant.

Therefore, the other plants need to ramp up quickly if the solar farm is suddenly covered by clouds. Think about unplugging a computer but the screen stays on and the system continues to function. The 'grid' needs to do the same thing. If it doesn't, system frequency may fluctuate and this could cause load shedding.

The system carries a certain amount of energy in reserve at all times. This is called spinning reserve. If a very large load (say 20MW) is suddenly cut from the system, or similarly, an equal amount of generation is taken away, you will see a large swing in frequency.

Put another way: Consider a car placed on a jack with its wheels spinning. Should it suddenly be dropped on to the road, the wheels will slow down dramatically. Speed, in this case, would be much the same as frequency. The car would need to be revved up almost instantaneously to maintain the power to its wheels.

Large vs small generating plants

Flexible fossil fuel plants also need to be sized correctly to make 'space' on the grid for renewable sources in order for consumers to see additional cost savings.

Despite the fact that a new large power plant could produce electricity more cheaply than existing plants, it would need to operate at full capacity and close to maximum all the time. That could use up too much 'space' and would not allow for increasing the integration of renewables on the grid.

Additionally, more than a dozen fossil fuel plants are already in operation and they would also have to reduce output to make way for newer, efficient generating plants, whether they are powered by natural gas or renewables.

As a result, some of these existing plants may not reach their 'sweet spot'. That is where a power plant generates electricity at the best cost to the consumer. This would mean that with new generating plants (base load and/or renewable), all the other plants feeding the national grid would have to reduce their output and operate at less economical levels, which would offset the benefit of a single cheaper resource.

The cost of energy will not depend entirely on the size of a new plant. It will depend largely on how well the new plant works with the existing plants for the best overall cost reduction on the system. In some cases of heavy renewable generation (such as California), the total cost of generating power has increased due to the inflexibility of a large base load unit.

We, therefore, need to make sure we install the best mix in terms of size, type, and flexibility of plants to ensure the best price and reliability of service to the Jamaican electricity customer.

Jamaica has total installed renewable capacity of just over 70MW. The Jamaica Public Service Company (JPS) has installed 32MW of wind and hydro power. Wigton has installed 38.7MW of wind. Another 78MW is scheduled to come on stream by 2016. Wigton will provide 24MW from its project at Rose Hill. The BMR wind farm will add an additional 34MW.

Content Solar will add another 20MW from its project close to Content Village, Clarendon. This does not include present and future rooftop solar resources, which further complicate the cost to integrate renewable energy as the location and size of the generation sources are unknown to the JPS.

Grid-connected renewable resources will provide about 150MW of Jamaica's capacity by 2016. Although this represents about 15 to 18 per cent of the installed system capacity, when considering the atmospheric intermittency of renewable technologies (rain, wind, and sun), these resources are expected to provide only about 10 to 12 per cent of the average total annual energy consumption of Jamaica.

Any planning for the next tranche of electricity generation must recognise that Jamaican power will be generated by both fossil fuel and renewable energy plants. That combination will be different from what it is now. The new plants will also be different from those in use now. The goals must be: dispatchable, flexible, reliable, and definitely cheaper.