Apr 8, 2015 | Scale Microgrid Solutions

Why Natural Gas is Key to Sustainable Solar PV Growth


Recently, Solar City announced their new GridLogic program, a turnkey “Microgrid-as-a-Service” solution. For many reasons, this program and others like it, are a huge step forward for the distributed generation market. But, while 2/3 of the major components of this service have been talked about at length within the alternative energy industry, the third and arguably most important component of the solution has received very little fanfare.

In my view, understanding the importance of the standby generator in this equation is of paramount importance to innovators in this space. Unfortunately, explaining the rationale behind this claim is extremely complex, so I’ve done my best to simplify this rationale for all via a technology I recently discovered called a notebook.

There is only one key takeway from this doodle (and for the record, I drew this on a train and it’s not meant to be to scale), but that takeaway is the key to successfully integrating solar PV into our current energy infrastructure.

As you can see, under a solar only solution, the example facility’s peak demand from the grid varies from 200 kW on sunny days to 500 kW on cloudy days. This variance is a nightmare for utilities, because they have to build enough infrastructure to support a 500 kW load. But, on most days, they are not coming anywhere close to earning the amount of revenue they would traditionally expect from a 500 kW facility.

There are only 2 primary solutions to this problem (that are realistic). Option 1 is for utilities to restructure their tariffs and increase their fixed demand charges. The problem with Option 1 is that it negatively incentivizes solar PV customers, which is in direct conflict with our country’s stated sustainability objectives.

Option 2 is the ““Microgrid-as-a-Service” approach. However, as you can see in my doodle, incorporating solar PV and battery storage is not sufficient to curb this problem in an economic fashion. Moreover, in the event of 2-3 cloudy days in a row, the battery does nothing to curb the facility’s monthly peak demand (most utility demand ratchets are calculated monthly). However, by incorporating a tertiary source of supply that is not correlated with ambient conditions (aka a natural gas generator), the facility can stabilize its peak demand throughout the month.

There are many technical subtopics to this conversation, but the purpose of this article is simply to help people understand why inclusion of “boring” natural gas generators is so important in this equation. This distinction is important for people to understand. Thoughts and comments are welcome.