Four laboratory prototypes are described in this report. Measured results and projected heat storage densities for units of 70 and 1000 kWh storage for single family houses are reported. All four prototypes are closed sorption units and act as thermally driven heat pumps. Two work with absorption: three phase absorption process (TCA) with LiCl-water, and two phase absorption with NaOH-water. Two work with adsorption, one with zeolite and the other with silica gel. The different technologies are at very different stages of development. The TCA technology is in the process of commercialisation by the Swedish company ClimateWell AB, and over 20 storage systems have been installed, mostly in Spain. A further 100-200 are planned for 2007. The other technologies are in the prototype stage with no companies intending to develop and market them. The Modestore store was developed in a European project, and the main company within the project (Sortech) is commercialising the technology as a heat pump with essentially no heat storage. The storage density for cold, when compared to water, is more favourable than for heat. For the ClimateWell 10 commercial prototype the storage density for cold is 4.7 that of water whereas for heat it is only 1.2 times greater. This is due to the fact that the temperature range available for water storage for cold is much smaller (~10°C) than for heat (~60°C). For short term heat storage, none of the technologies have a significant advantage compared to water in terms of storage density. The energy density can only be slightly greater than that for water, mainly due to the space required for heat exchangers and other components. In addition all of the storage systems lose heat during the charge and discharge process due to irreversibilities in the processes themselves. Most of this is due to the different temperature levels of charge/discharge and the related sensible energy between these. For longer term storage (1000 kWh) the energy density for the TCA technology and NaOH storage systems is nearly three times that of water. In addition, once the sensible heat from the solution has been lost, the energy can be stored indefinitely, a significant advantage compared to water. In terms of material cost, all materials are expensive compared to water, with NaOH being by far the least expensive. The cost for the whole storage system has not been estimated here. For the ClimateWell 10, the projected cost is ~8000€ for a heat pump system consisting of two units in parallel, with a total heat storage capacity of 70 kWh.