The invention relates to a method for preparing a hydrocarbon by reducing CO.sub.2, wherein CO.sub.2 is reduced to a hydrocarbon with the aid of a directly heated electrode. A device for carrying out a corresponding method, a corresponding power plant and a system comprising said power plant and a vehicle with a combustion engine are also objects of the invention. The method and device may, e.g., be used as a micro-energy system for decentralized energy supply.

A combined heat and power plant for the decentralized supply of power and of heat may include at least one prime mover for providing electrical energy while providing waste gas, at least one thermal store for storing thermal energy provided by the waste gas, and at least one high-temperature battery in which the electrical energy provided by the prime mover can be stored. The high-temperature battery can be supplied by the waste gas provided by the prime mover to keep the high-temperature battery warm.

A novel method is described for room heating using stored solar heat. Solar heat is stored in an insulated tank by using scrap and inexpensive heat absorbing or heat storing materials. Stored heat can then be extracted by air circulation for room heating. The temperature of the room air is controlled by a thermostat. When the room temperature drops below the set point on the thermostat, a circulating air pump turns on and extract the solar heat until the room temperature air reaches the desired set temperature. Once room temperature reaches the set point in the thermostat, the air circulation pump turns off.

A distributed solar power generation and hot water supplying system includes: a photovoltaic power generation self-service sun tracking system, an inverter, a controller, a storage battery, a heat-exchanging water tank and an electric heater provided therein, wherein a solar battery and a solar collector are mounted on the photovoltaic power generation self-service sun tracking system, an electricity output terminal of the photovoltaic power generation self-service sun tracking system is respectively connected to an inversing input terminal of an inverter and a surplus power supplying input terminal of a controller; an MCU-controlled power output terminal of the inverter is respectively connected for off-grid power consumption or grid-connected power generation, and to an inversing output terminal of the controller; a charging/discharging control output/input terminal inside the inverter is connected to an input/output terminal of the storage battery and a storage battery power supplying input terminal of the controller.

A solar water heating pump system. A heat pump and a heat exchanger, connected to the heat pump, and creating heat that exchanges heat from the heat pump to change a temperature in a load, which is usually heated or cooled water. There is also a connection to grid power. A controller controls the heat pump and heat exchanger based on the grid power and detection of an amount of solar power that is available.

Solar electricity is used more efficiently and at lower cost via the technique of interrupted DC power. Interrupted DC removed the spark problem from high voltage DC circuits, allowing their use with normal appliances. Wasteful and expensive inductor based voltage changes were avoided by adjusting solar panel output voltage via loading. This provided prioritization of use among appliances. Furthermore, the extreme decrease in sparking obtained by interrupted DC allows for the manufacture and use of lower cost direct current circuit breakers that are self powered and provide protected circuits of greater than 99% direct current purity.

This invention provides a system and process to optimize photovoltaic (PV), grid, and other electricity in powering an electric water heater. The system comprises a photovoltaic (PV) controller coupled to a plurality of power input sources and heating elements wherein the heating elements immersed in an electric immersion heater water tank. The PV controller is further configured with control circuitry having an operating efficiency routine calculating optimal use cases from a variety of installation parameters and learned parameters to determine the appropriate power input source and switch between sources accordingly.

A system including a photovoltaic panel having a first heat exchanger for absorbing heat from the panel and/or from the environment by a heat exchanging fluid, connected to a heat pump. A second heat exchanger is provided for absorbing heat by the heat exchanging fluid and a control means for controlling a flow of the heat exchanging fluid through the first heat exchanger and/or the second heat exchanger. The heat pump is arranged to cool the heat exchanging fluid. The system has the following operating modes: a first mode in which cooled heat exchanging fluid is fed to the first heat exchanger; and a second mode in which cooled heat exchanging fluid is fed to the second heat exchanger and then fed to the first heat exchanger.

A hybrid supplemental solar energy collection and dissipation system with one or more heat pumps is featured. The system includes one or more commercially available photovoltaic panels configured to convert incident radiation to electricity. One or more supplemental solar energy collectors having a flow of fluid therein are selectively coupled to the one or more photovoltaic panels. The one or more supplemental solar energy collectors are configured to collect thermal energy from the one or more photovoltaic panels, radiate thermal energy to space, collect thermal energy from the environment and/or dissipate thermal energy to the environment to heat or cool one or more loads. One or more heat pumps are coupled to the one or more supplemental solar energy collectors and the one or more loads and are configured to amplify heating and/or cooling of the one or more loads.

A solar thermal assisted water heating system includes a thermal collector comprising a plurality of fluid channels configured to collect heat from a surface of a photovoltaic module, a drain-back tank coupled to the thermal collector, a first pump coupled to the drain-back tank and configured to pump fluid from the drain-back tank to the thermal collector, a first heat exchanger configured to receive fluid from the thermal collector, a heat pump coupled to the first heat exchanger and configured to remove heat from the fluid and heat water with the removed heat, and a controller configured to control the first pump and heat pump. The system may include a photovoltaic module and a hot water tank. These systems improve the efficiency of water heating, and the drain-back tank may serve as a thermal battery that stores heat and provides the stored heat when environmental temperatures decrease.