More infos : http://www.solardishsystem.com/
Salt can store up to 7 times more energy than water (in same space) so I use an insulated beer bottle box surrounded with compacted salt and in the middle, there are 600 ml aluminium cans filled up with burning canola oil (250 degrees celcius). Heat is transferred from the oil to the aluminium to the salt and stored in the insulated box. Tap water is preheated to more than 60 degrees Celcius. This system combined with a 6' solar concentrator could be a cheap solution to store solar energy for most of the time all year long. In this experiment, 24 hours later the salt was still burning hot.