Sandbox battery to energize remote mines

Solar energy company and startup from Massachusetts Institute of Technology, Solar247 Inc., announced earlier this year a robust new battery technology, HeatStorE, a long duration thermal battery designed to offer a reliable, renewable energy storage alternative to the conventional diesel engines powering remote mines, villages, and micro-grids.

"In the mining industry, we see more and more off-grid microgrids that incorporate short-term energy storage systems," said Thomas Hillig, managing director of microgrid consultancy THEnergy. "As the market is maturing, we see that miners are ready for the next step and increase the share of renewables – in the long run also 24/7-operations without gensets. This is what they need long-term storage for."

The basic principle of 247Solar's thermal battery is simple; electric resistance coils heat an inexpensive thermal storage medium – in this case, silica sand – using low-cost excess electricity from sources such as intermittent solar and wind power generation.

The excess energy is stored as extreme heat – up to 1,000 degrees Celsius or 1,850 degrees Fahrenheit – at a fraction of the cost of batteries. Whenever needed, a specialized turbine reconverts the heat to electricity. Unique to the technology, the turbines can do this without combustion, as atmospheric-pressure air is passed through the thermal storage and drives the turbine to generate electricity.

"HeatStorE combines two inventions that are part of 247Solar's Ultra-High Temperature Technology Platform, the 247Solar Heat2Power Turbine and the 247Solar Thermal Storage System," said 247Solar CEO Bruce Anderson. "Combining these two proven technologies ensures that HeatStorE is also extremely reliable. We expect more than 20-year operations with little or no performance degradation."

Heat2Power, a 200 kilowatt-electric turbine made by Capstone Turbine Corp. and modified to 247Solar specifications, is powered directly by ambient-pressure hot air – not steam.

To make the system more reliable, the thermal battery can be recharged with a combustor that burns gasoline, diesel, biomass or hydrogen – the latter being the best choice for achieving the overall goal of reducing emissions.

This innovative approach is designed to replace traditional diesel engines at remote mines, as it can provide 24/7 reliable operation with higher renewables efficiency, significant fuel savings, and dramatically lower operating costs over a lifespan measured in decades.

Due to its remarkably simplistic design and relatively inexpensive production costs, HeatStorE can potentially be a gamechanger for remote mining operations seeking to reduce emissions and maintain appropriate energy requirements.

Considering that the new approach consists of a factory-made, shipping-size container filled with sand heated by resistance coils, its robustness is no surprise. Neither is its low operating and maintenance costs. The combinations of robustness and life-cycle cost advantages will enable mining companies to implement new power plant concepts with fewer diesel engines – ultimately without any at all.

The new thermal battery can also be used in applications other than mining, such as community microgrids, off-grid villages, or island grids. HeatStorE is ideally suited to provide operational flexibility and resilience.

The typical storage duration is in the range of 4-20 hours, which also allows for substantial grid support and load shifting, interestingly, the cost per kWh drops rapidly with duration, and behind the meter in industrial applications, the battery can also convert otherwise-wasted hot process exhaust to electricity.