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.
The Cowessess First Nation High Wind and Storage Project comprises a single 800-kW utility-scale wind turbine operating in combination with a 400-kW ESS. Credit: Saft.
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.
Making the Most of the Arctic Circle’s Midnight Sun
The remote community of Colville Lake, 50 km north of the Arctic Circle, is home to about 160 people. It is only accessible by air or by ice roads during a six-week window in February and March. For some years, its electrical power requirements – 150 kW peak load and 30 kW base load – has been met by diesel generators. However, NTPC (Northwest Territories Power Corporation) the power utility that serves 43,000 people spread across 33 communities in northern Canada is now transforming the region’s power supply to cheaper, cleaner and more reliable renewable energy.
In 2015 a microgrid was deployed at Colville Lake that combines solar panels with new diesel generators (2 x 100 kW and 1 x 150 kW) and an ESS. The 136-kW solar panels generate around 112 MWh a year. The solar output exceeds the community’s average electricity load. Therefore, the primary goal was to reduce the runtime of the diesel generators, especially in the summer when the sunlight is available for virtually 24 hours a day.
A key requirement for the ESS was to withstand the harsh variations in local temperature from -50 ˚C to +35 ˚C. NTPC also wanted to ensure maximum value for money with an ESS of the optimum size to balance its capacity and cost versus the size of PV panels and fuel savings.
Saft’s team used advanced modeling to identify both the optimum size of the ESS and the solar array. The resulting ESS comprises a containerized Intensium Max 20M Medium Power container with 232 kWh energy storage capacity and a 200 kW Power Conditioning System. It features a special cold temperature package that combines layers of high-tech insulation with a hydronic heating coil that makes use of the same hot glycol that maintains the diesel gensets at operating temperature. This minimizes the cost of keeping the battery in its optimum temperature range.
Colville Lake’s solar PV system. Credit: Saft.
The main role for the ESS is to support the network frequency and voltage. This allows the diesel generators to operate at their point of maximum efficiency and to be shut down whenever possible. The reduced runtime provides significant savings in diesel consumption. It also reduces maintenance costs as there is lower wear and tear on the plant when it is run at a steady set point, rather than ramping up and down to meet short-term load variations.
High Wind and Storage Project Delivers Clean Power for CFN
Just south of the TransCanada highway in Saskatchewan, the Cowessess First Nation (CFN) has developed its High Wind and Storage Project to harness the abundant but intermittent wind power of the prairie. It comprises a single 800-kW utility-scale wind turbine operating in combination with a 400-kW ESS including two Saft Intensium Max 20E battery containers.
Since the system was commissioned in 2013, the grid‐connected ESS system has proved its capability to help optimize renewable wind power performance by increasing reliability and decreasing volatility by as much as 70 percent. The primary function of the ESS is for wind smoothing. It can achieve a ramp rate of 10 percent per minute of the wind turbine output while also providing up to 400 kWh of peak shaving capability.
The system is acting as a model for other First Nation communities across Canada. And if its long-term performance continues to meet expectations, wind energy storage technology could soon be cost competitive with energy from clean coal or clean natural gas.
Stabilizing the Faroe Islands Grid as Wind Power Increases
The Faroe Islands, situated halfway between Norway and Iceland, is committed to reducing its dependence on oil by making use of its abundant wind and hydro energy resources. The aim is to increase the share of renewable generation from 38 percent in 2011 to 75 percent in 2020 as the country’s overall energy consumption continues to grow.
A new 12 MW wind farm, comprising 13 wind turbines, located in Húsahagi on the island Streymoy was inaugurated in 2014. It increased the country’s wind share to 26 percent of total electricity production.
In 2015, SEV (the power producer and distributor for the Faroe Islands) commissioned a major ESS project to capture the full potential of the new wind farm. This was Europe’s first commercial deployment of a Li-ion battery system operating in combination with a wind farm.
The 2.2-MW, 720-kWh ESS comprises two Saft Intensium Max High Power systems combined with a power conversion system and power control system. Its main function is to address key grid stability issues as SEV increases the penetration of intermittent renewable energy resources by providing ramp control, as well as frequency response and voltage control services. This helps minimize curtailment (when wind generation is available but not injected into the grid) which can otherwise occur in periods of high wind and low consumption.
The Colville Lake ESS is comprised of an Intensium Max 20M Medium Power container with 232-kWh energy storage capacity and a 200-kW Power Conditioning System. Credit: Saft.
Remote communities worldwide are making the transition from diesel generation to greener and more cost-effective renewables. However, the inherently intermittent nature of solar and wind power presents challenges in maintaining a resilient and reliable supply of electricity. Large scale Li-ion energy storage is now proving its capability to address the key grid integration issues of frequency regulation, ramp rate and curtailment.
Michael Lippert is business development manager for energy storage at Saft.