Pumped storage of energy from ambient temperature changes

In the latest iteration of my nearly-reversible no-solid-moving-parts heat engine design, I aim for a machine installed at a pumped storage site with lakes at two elevations and an existing hydroelectric pump / generator. The heat engine will pump water upward whenever the ambient is hot enough to provide excess energy, and will temporarily compress cold air when the weather forcast says the current temperature is at a minimum.

[still working on this.  A (hopefully small) second upper reservoir, slightly higher (or lower) than the upper lake is needed.  During compression, every other tank is completely full of water.  Air is moved from one tank to the next lower tank by connecting them at the top and letting water flow from the slightly higher reservoir into the higher tank, displacing the air into the lower tank and water from the lower tank up into the other upper reservoir. Not nearly as clear as the system with multiple reservoirs but multiple tanks has many advantages]

Because all compression and expansion must take place while connected to the same upper reservoir, a single working-gas tank will not suffice. The design specifies a series of tanks, each connected from its bottom port past a water pressure gauge and through a valve to the upper reservoir by a dedicated water pipe sufficiently large to avoid turbulent flow during expansion and compression of gas in the tank. The resulting system has a larger surface area devoted to heat exchange, and hence produces more power than the earlier design. Also, a tank used with a wide range of pressures repeatedly expands and contracts, and so might have a shorter useful life than many tanks each dedicated to a narrow range of pressures.

Heat sinks and sources are attached to the tanks by gravity-feed heat pipes. The heat sink, used during compression, is located above the tank. Heat pipes extend downward from the heat sink into but not through the tank. Liquid refrigerant in the bottom of a heat pipe evaporates as working gas warms due to work done on it during compression, and condenses at the relatively cool top of the heat pipe, delivering heat to the heat sink. Valves in the heat pipes are closed when the tank is not producing heat. A chimney above the heat sink carries lighter hot air upward, supplimented with a fan if necessary.

The heat source, used during expansion, is located below the tank. Heat pipes extend upward from the heat source into but not through the tank, delivering heat to relatively cool gas inside the tank as the working gas cools after doing work on the rising water. Valves in the heat pipes are closed when the tank is not consuming heat. A flue extending downward below the heat source carries heavier cool air downward. A fan is available if necessary.

A large high-pressure gas conduit runs from the top of each tank to the next, with one valve beside each tank, so that any pair of adjacent tanks can be connected by closing the flanking valves and opening the central valve. Thus, each tank is directly connected to a water pressure gauge and three valves, including the water valve at the bottom, and two gas valves at the top.

During a time of low temperature, … [still working this out. Having tanks at different levels makes it complicated…]


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