SolarCoin isn't intended for energy trading, it's a pure incentive. This is quite smart as it skirts all the different regulation heavy national energy policies, and allows it to expand unimpeded. The use case for SolarCoin is a global currency that is 10 times faster than Bitcoin, uses hardly any energy to operate and is initially distributed to producers of solar energy (itself a highly distributed energy source).

A real problem for energy trading coins is a lack of block-chain compatible and secure metering equipment, manually loading meter readings is not scalable and the potential for fraud is huge. This issue will need to be solved for every energy supplier in each nation before those projects can gain traction, effectively needing a second or third global smart meter rollout.

My view is that the SolarCoin model is far more realistic in the short/medium term as it's barriers to entry are far lower.