Solar Power May Be the Least Expensive Energy Option for Microgrids

In the spring 2017 issue of the Sierra Atlantic I shared my personal experience regarding solar power: powering my home (heating/cooling/lights/electronics/hot water) for a third of the price of fossil fuel-generated electricity. Like many others, I elected to use the electric grid as my storage medium. At some point, I will switch to battery storage to meet some or all of my storage needs. Currently, however, grid “storage” is an interplay of solar, wind, hydro, nuclear and fossil fuels balancing out loads at various times of day and seasons.

Given the variability of both the load and the supply side, the standard approach has been to overbuild generation capacity at considerable expense. Coal-burning and nuclear plants can take many hours to change their output. For that reason, these power sources are reserved to provide base-load power, the minimum power required for low demand periods.

Combined-cycle natural gas plants can change more quickly but still require many minutes, even hours, to adjust. Specially designed “peaker” natural gas plants are quicker in their response times, taking only a few minutes. In the past, power companies have turned to natural gas to respond to peak demands. The decline in natural gas prices has resulted in a push to replace coal with natural gas for base-load supply as well.

A more recent development has been a move toward “microgrids” — a small network of electricity users with a local source of supply that is usually attached to a centralized national grid but is able to function independently. This movement away from large, centralized power sources has been yet another benefit of the growing use of renewable energy. Keeping power generation local has meant fewer dollars drained from the local economy. Microgrids reduce line loss, are more stable, more resilient and less susceptible to massive power outages. In short, networked microgrids are the grid of the future.

One caveat: solar and wind energy generation is variable as a rule and must be compensated for. A microgrid that is constantly turning to the national grid to smooth out its supply is not truly taking advantage of what a microgrid design has to offer. The predominant strategies used to even out supply are backup natural gas-driven turbines and energy storage in all its multiple forms. While natural gas peaker plants work better than coal-powered plants, taking only minutes instead of hours to respond, energy flow from battery storage systems can be turned up or down in fractions of a second. The other obvious disadvantage of natural gas plants is that they perpetuate our dependence on fossil fuels and the environmental damage they cause.

While energy storage technology is still in its infancy, many businesses and researchers are working on increasing storage efficiency and decreasing the cost. Just as photovoltaic solar panels saw efficiency double and cost drop 60% in the last decade (http://news.energysage.com/solar-panel-efficiency-cost-over-time/), many see similar strides in storage systems in the near future. The good news is that, in many circumstances, storage systems have already advanced to the point that they surpass natural gas peaker plants as the system of choice when developing microgrids.

The advance in storage systems is good news, because even though we might be living with legacy fossil fuel technology and infrastructure for some time yet, new and replacement projects can now use renewables accompanied by storage systems, hastening our transition from fossil fuels. It’s for this reason that the Atlantic Chapter has taken the position of “no new fossil fuel infrastructure.” It’s simply not needed and would only serve as a dangerous distraction and waste of valuable time, money and resources better spent on building a better, healthier future.

In the Northeast, the typical day’s high demand for electricity is about 150% of low demand. The high demand period happens to coincide with daylight times and early evening. In the past, natural gas peaker plants were used to cover the difference, at an average of $191/MWh (megawatt hour). Competing with this is solar at about $53/MWh, when the sun shines, and solar storage at $92/MWh when it is not.

With decreased cost of solar power, the shift to solar has already been underway for a number of years. With the added impetus from lower storage costs, we can now expect a more rapid shift away from natural gas to supply peaking power as well. New York State in particular, with its aging infrastructure, is ideally situated to take advantage of this new technology. Strategic storage systems might even prove more cost effective than increasing line capacity in the more rural areas of our state.

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