New battery technology

Barium-titanate ultracaps. 

2007, MIT Technology Review:

A new ultracapacitor technology by EEStor is claimed to store 10x the power of a lead-acide battery at half the cost and is superior in terms of energy density, price, charge time and safety. Ultracaps, as they are sometimes called, can store and release energy an almost unlimited number of times, or more times than current rechargable batteries anyway. It uses barium-titanate powders.

Energy cost comparison to drive 500 miles:

1. Gasoline: $60
2. New EESU ultracap: $9

Alas, Wikipedia says the claims were 100x what the actual results were.

Bloom energy cell

Google has been testing the Bloom Energy cell which takes natural gas (and oxygen from the air) as input. Google has been testing it since 2008. The BEC does not use combustion to create energy. It's being tested by other large companies all over the world like Johnson and Johnson, AT&T, Nokia, Bank of America, Caltech, Adobe, Dreamworks, Ebay, Honda and Panasonic.

An "energy cell" can be combined into an "energy stack", and these can be combined into an "energy server". Energy servers are installed onsite so electricity doesn't have far to travel in order to be used.

Here's model UMP-571, which weights 5000 lbs and outputs 200kw at 480vac. It seems a bit big for home use as US homes take 120vac.

Lithium air battery could have big gains

Extreme Tech, Oct 2015. There's a chart here which shows on one axis, energy density by liter of volume, and the other axis shows energy density per kilogram. Lithium batteries have their advantages (no recharge memory) they also have disadvantages (sudden explosions or fire).

Quantum batteries

ExtremeTech, Aug 2015. Go and read it. Two entangled qubits can actually store energy. Neat.