AES and battery power

El Nueva Dia had an article yesterday about a report on battery power for PREPA.
As usual for the, the info was not particularly useful. Why can't they find writers that understand a bit about technology. But that is another discussion.

The article is here
https://www.elnuevodia.com/negocios/economia/nota/aesproponeunanuevaredelectrica-2381226/

It basically said that AES, who we know for the clean coal plant in Guayama, wants to install utility scale (multi-megawatt) batteries in PR. These would be used in conjunction with solar panels, though that was not clear in the ND article. Sounds like a good idea and I wanted to know more.

I contacted AES press office to request a copy of the report. They  replied within an hour with a link to the report and links to additional information.

The report can be downloaded here: http://energia.pr.gov/wp-content/uploads/2017/12/IN20170002A30-COMENTARIOS-AES.pdf

I read through it last night and it had some very interesting and useful information on micro and mini-grids and how they might be implemented in Puerto Rico. One of the major problems with solar and wind is that it is inconsistent. In the case of solar it is only available about 8 hours a day (average over the year). If it is ever going to be useful, some sort of storage is needed. Batteries look like the main technology at the moment, though there are some other options.

I had always assumed that batteries would be sized so that they could be charged during the day (or when the wind is blowing in the case of windmills) and then have enough capacity to cover the downtime.

Reading the AES report, it seems that this is not the strategy. AES proposes that batteries be sized for about 5 hours. They would be charged up during the day then discharged to cover peak demands in the evenings. This is pretty beneficial in itself because it adds stability to the power system, allows matching of generation during the day with consumption in the evening and some other factors detailed in the report.

It is a useful addition to the grid but does not replace the need for baseload generation by fossil fuel (coal, gas, oil), nuclear or some other large scale generation. It will replace peaking systems such as gas turbines but not the central plants.

The report has limited information about the economics of the system. I am wondering if, considering the cost of batteries, controls, solar panels, windmills and so on the system makes economic sense on its own. It may make economic sense only due to tax credits, deductions, subsidies, preferential buyback pricing (eg; net metering).

It may, but I could not tell from the report.

AES is to be congratulated for a very interesting proposal and if anyone can make the concept work, I would think they can.

I strongly recommend that anyone interested in Puerto Rico's energy future read the report.