Hydrothermal Challenges – Heat Sources and Heat Sinks

Lightbulb Balloons

This post is where we start to answer the question “If there’s so much energy in the ocean, why is it so hard to use?”

A basic understanding of thermodynamics, heat sources, and heat sinks is essential for understanding how hydrothermal power works, its challenges, and our new approach to making it effective and affordable.

To understand what thermodynamics means, let’s break it into parts:

  1. Thermo – Heat
  2. Dynamics – Having to do with movement

Thermodynamics is the study of the movement of heat energy. Unless heat moves from one place to another, we cannot do anything with it.

For any heat engine to work, including fossil fuels, geothermal, hydrothermal, and some types of solar you must have a heat source and a heat sink.

Imagine a container of warm fluid. This is our heat source. Imagine a second, cooler container of fluid. This is our heat sink. Imagine opening a tube between the two containers. The heat energy of the warmer container will transfer into the cooler container until they reach the same temperature.

You can use this heat flow to perform work. Take a balloon above a lightbulb – the air inside the balloon expands as the light bulb (heat source) heats it. When the balloon is removed from the light bulb the air in the balloon cools, releasing its heat into the surrounding air (the heat sink). The expansion and contraction of the air in the balloon is the work performed.

Heat sources and heat sinks are at the core of hydrothermal power systems. Generally the heat source is warm water near the ocean’s surface, and the heat sink is cool water deep below. Generally the heat transfer powers a piston through the expansion and contraction of a working gas as heat flows through it.

Here is the challenge:

There are physical laws that govern the amount of work that can be done during the heat transfer. We will discuss these laws in detail later (Rankine and Carnot Cycles). The short version is the higher the temperature difference between source and sink, the greater the efficiency of the system.

Greater temperature difference = more work performed = more electricity generated

Smaller temperature difference = less work performed = less electricity generated

This is why burning fossil fuels has thus far held the advantage. The temperature differential in a coal power plant is over 500 degrees Celsius, compared to 5-20 degrees in a hydrothermal plant. Using conventional methods, burning things is always going to produce more power. As a result coal power has been more effective and affordable in generating the power we need, even though the global coal energy reservoir is so much smaller than the hydrothermal energy reservoir.

Fossil fuels = limited resource with high temperature differential

Hydrothermal = unlimited resource with low temperature differential

This gets to the root of what we are doing at Equilibrium Energy. By reframing the rules we intend to bring hydrothermal power into its place as an affordable renewable resource. Our method appeals to physical laws that have not been considered for this application in the past. We think of power generation through hydrothermal sources as fundamentally different from fossil fuel source and have patented a new method that is uniquely suited for a small temperature differential with an unlimited heat source.

What is this new method? More to come…

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