Until recently, the world’s most remote off-grid communities have relied on traditional diesel generators to supply their electricity needs. This has created significant cost and reliability issues. Sometimes, it can cost more to transport the fuel to the site than it actually cost to purchase in the first place. Should adverse weather disrupt travel then there is a risk of running out of fuel. Furthermore, the gensets need regular expensive maintenance.
For these reasons a growing number of communities are now turning to solar photovoltaics (PV) and wind turbines. And in many cases, they are adopting microgrid solutions in which the diesel generation and renewable plant complement each other. The aim is always to ensure the reliability and autonomy of the electricity supply and to optimize operating costs.
This is where a large scale lithium-ion (Li-ion) energy storage system (ESS) can play a vital role in mitigating the variable and unpredictable nature of wind and solar plants. The ESS can perform a number of roles, including control of ramp rates, power smoothing, power shaping, peak shaving and frequency regulation.
It is useful to consider the situation at a typical remote site. Using standard power electronics a PV installation might contribute up to 20 to 30 percent of the power that would be generated by the diesel genset during daytime hours. If we add dedicated software then the PV penetration could increase to 50 percent. For example, a 1-MW microgrid might accept up to 300 kW, but this could be raised up to 500 kW of PV in the best case. Since the PV output is limited to sunlight hours, highly variable and does not necessarily meet the required consumption profiles, its contribution to the overall energy mix is naturally limited.
However, when an ESS is introduced, it is possible to maximize the contribution of renewables, increasing the penetration and harvesting all of the PV power. Fuel savings of 50 to 75 percent then become a realistic possibility.
Three recent examples show how energy storage is now making an important contribution for some very remote communities.
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