The grid as an emergency supply?

It’s official. Finally Spain has the most toll-intensive consumer power generation (what is called self-consumption) law in the world. The so-called “sun tax” is in place.

It is important to understand the worries of the regulator here;

Given the high fixed costs of the system, further reductions of electricity demand (as with self-consumption) increase the price of energy in a Grid independence cycle. The goal of increasing the toll on self-consumption is to ensure the system costs are covered, delay the implementation of self-consumption (starting in the islands and small systems), delay consumer energy storage (in fact it is also a “battery tax”) and (try to) avoid further political problems. Of course, it is not the best solution, academics and regulatory experts agree that politically fixed costs that have to be paid by all citizens shouldn’t be in the tariff but evenly paid from the nation’s bugdet (like the extra-costs for electricity in the islands).

Image by Cancia Leirissa on freeimages.com

“Grid Emergency Exit”                                                       Image by Cancia Leirissa on freeimages.com

What are the consequences? Rising prices, and the fact that fixed costs (for the contracted power) are surging, push the active consumer to look for the following solutions:

  • The first is to increase electricity use efficiency and install energy efficient equipment, but if fixed costs are very high, the result is small reductions on the consumer’s bill.
  • An alternative is of course to reduce the contracted power, but prices will continue to grow to avoid these “unsupportive” people to affect the system revenues.
  • Other is to go completely off-grid. (We should highlight that at least in the law there is no tax to maintain the grid for those off-grid despite them being “unsupportive”)
  • Finally, in between the previous two options is partial off-grid, while reducing contracted power at the same time.

What is the risk of too much off-grid? It means excessive and underused installed solar and battery (typically with today’s technology) or worse, the use of diesel gen-sets. It also means an underused grid system and generation units (if these are coal it’s ok, if off-griding causes utility scale renewable energy spilling then it’s less sustainable).

Another intermediate solution is to have more flexibility and innovate in power supply contracts. In Spain there is the possibility of emergency power supply, so a consumer could reduce the system size and use the grid for limited hours, while the rest of the year he would be a disconnected microgrid.

There is a drawback to this solution, as these limited hours could be simultaneous to all the solar islanded microgrids, which means a lot of underused power capacity in the grid just for emergency. If we look at the network as a whole, is it less costly than installing excess capacity and storage in the prosumer microgrids? If the network capacity used is hydro and wind it is preferable to more solar and more bateries in the consumer microgrid, but if the grid needs centralized diesel or other peaking power plants, then it might not be.

A different grid supply mode is possible, where the contracted power is the minimum and it is only used to charge batteries, very slowly. This would not put such an emergency peak stress on the grid system but the opposite, ensure a completely flat “super-predictable” load (however, as explained earlier in this post a flat demand is not ideal) A system called SARA, where the batteries charged by the grid are always isolated from the consumer microgrid was developped in 2014 with this goal.

http://www.suelosolar.com/newsolares/newsol.asp?id=9843

Source: Suelo Solar

Another benefit of this solution is that the prosumer microgrid could be a Five Start Direct Current microgrid to achieve maximum efficiency.

We may conclude that, although the regulatory framework should drive towards sustainability, when it is not the case, more innovative approaches are needed.

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