The main objective of the project is the development of several reliable, safe, high efficiency and high capacity heat pumps working with the two most promising natural refrigerants: Hydrocarbons andCO2, together with a set of improved components and auxiliary devices adequate for the efficient and safe use of the two refrigerants.The project aims to reach a higher efficiency (10-20% SPF improvement) and lower Carbon footprint (20% lower TEWI) than the current state of the art HFCs/HFOs or Sorption heat pumps. The costs shall be very similar or slightly higher than the latter systems (10%). The project will also focus on the development of an efficient capacity modulationin order to enhance the integration capability with other renewable sources in the energy systems of Buildings and Industry. In this sense, if the project is successful, it will clearly bring a definitive step forward to overcome the barriers holding back thespread of natural refrigerants by proving that a new generation of heat pumps based on HCs and CO2 is perfectly feasible and commercially competitive.The first objective of the project is the identification of the cases in which the use of Natural refrigerants can lead to cost effective and high efficient solutions with a fast commercial exploitation. The following cases have already been identified for their potentialinterest:- Hydrocarbons (HCs): air or water to water heat pumps supplying hot water at (40-50ºC) for heating applications as well as to produce sanitary hot water at 60ºC.- CO2: heat pump of high capacity to produce sanitary hot water at 60ºC directly from city water (10-15ºC). Designs with higher temperatures in the range 70-90ºC should be also explored.The project involves 6 key industrial partners (component manufacturers and heat pump manufacturers) who will strongly cooperatewith the RTD partners in order to achieve the targeted goals as well as to evaluate the necessary costs and measures to successfully bring the developed technology to the market.