Batteries (energy storage) – Ok, so I could write a lot about this. Batteries and their changing chemistries and emerging opportunities, and reduction in price were recently the subject of a report by Slade (2015) as a part of the DFID evidence based checking of this proposition. There will be many and myriad opportunities for choosing the right chemistry, the right configuration, the right lifetime/price point.
In this blog I want to outline only three points on batteries.
- What do we know? That Lead based batteries are currently cheaper per stored kWh than Lithium Iron Phosphate. However by the time you take the greater cycling of the Lithium based batteries, the lifetime cost per kWh of Lead and Lithium are pretty much of the same order. By 2020, the Lithium will be significantly cheaper.
- What do we know? That there are emerging chemistries that might become even more appropriate and cheaper. We have recently acquired a Sodium based battery that is higher in price than Lithium, but is said to have many more lifetime cycles, thus making its lifetime cost per kWh stored again of the same order. It is lower energy density and therefore more bulky but it is more disposable and unlikely to suffer from ‘lithium shortage’.
- What do we know? We know that we don’t know the lifetime of lithium batteries working in higher ambient temperatures and with rapid discharge rates. This is the one bit of technical research that needs t be done. Slade 2015 suggests that we shouldn’t trust manufacturers data and that some independent testing should be done.
However, moving into the future we acknowledge that batteries and their role in energy systems is a hot topic. Tesla and Moxia are both now selling lithium based storage for households who in the west want to use their (grid connected) solar energy more effectively and efficiently. The car industry is using lithium based batteries and there are millions being invested in research. So the efficiency and effectiveness of batteries in the PV-ecook proposition is being driven by external factors and is not dependent on there being a large ecook industry.
There are some alternatives to electrical energy storage. Nottingham University has been exploring phase change material in this context, and we recently explored this further. The challenge with phase change storage is that while it is lean and perpetuates the benefits of clean cooking, it takes away the link through to ‘modern energy’. Batteries and electrical storage could lead on to other uses of the solar for productive uses (and quality of life uses). Converting the storage to phase change material potentially reduces those possibilities. ON the other hand, reduces the waste problem, and potentially could be cheaper in the longer run.
- What do we know? That using a solar panel to phase change a material is possible, and that the material can old enough heat to boil water. Currently the cost of enough material to store the same energy as a 1.2 kWh battery, costs about the same as a 1.2 kWh battery!
- What do we know? Its worth exploring further as an alternative strategy!