Repurposing Thermal Energy: Home Climate Control, Car Parks, and Computing

The global thermal energy storage market may reach US$8 billion in 2030 from a size of US$4.4 billion in 2022, which is a Compound Annual Growth Rate (CAGR) of approximately 7.7%. The expanding demand for storage indicates a consistently growing usage of thermal energy. 

But what exactly is thermal energy, and how do we store it? We will delve deeper in the coming segments to get to the bottom of these questions to see how thermal energy is creating efficient energy usage paradigms for our modern world needs. 

The Brief History of Thermal Energy

The history of recognizing thermal energy and its potential dates back to 1847. The credit goes to globally revered English physicist and mathematician James Prescott Joule. 

To put it simply, Joule uncovered the relationship between heat and mechanical energy to eventually reach the law of conservation of energy, also known as the first law of thermodynamics. The law states that energy can be converted from one form to another but cannot be created or destroyed. 

How scientist Joule reached this game-changing conclusion was an exciting experiment that could help us comprehend the nature of what we know today as thermal energy. 

In his experiment, Joule measured the amount of work an electric motor should do to raise the temperature of a certain volume of water by one degree. He also measured the temperature increase in water when it passed through a perforated cylinder and the heat generated in compressing a gas. 

During his research, he found out the amount of mechanical energy applied to the fluid was always equal to the heat energy generated, indicating that repurposing energy is possible in one form to another. 

In broader terms, the experiment said a lot about our universe and its energy system. It showed, most importantly, that the entirety of the energy in the universe stays at a constant, with one form of energy converting into that of a different form. 

Joule's discovery gave birth to a full-fledged stream of study known as thermodynamics. We have seen the paradigm's first law already. It has three more laws. These four basic laws set the contours for thermodynamics that deal with heat, work, and temperature and how their interdynamics impact the notions of energy, radiation, and physical properties of matter. 

It is crucial to understand thermodynamics if one has to fully comprehend the potential of thermal energy and the ways it could help our processes. At its core, thermodynamics explains how thermal energy converts to other forms and vice versa. Thermal energy comes from thermal heat produced by particle movements within an object. The faster the movement, the greater the heat generated. 

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The Science Behind Thermal Energy Generation: Conduction, Convection, Radiation

Moving particles or molecules give birth to heat. But there are at least three ways in which these movements can generate heat. 

In the conduction process, heat is generated out of the movement of the constituent particles without the body moving. A real-life example of heat generation by conduction is the increase in temperature in a stainless steel spoon when it is put inside the cooking pot for some time while the pot is still being heated from below. 

The convection process is where the energy transfer happens between a solid surface and a moving liquid or gas. Heating water by putting it inside a pan and applying heat directly to the pan is an example of the convection process of energy transfer. 

Finally, in the radiation process, for heat or thermal energy to be exchanged, two bodies or substances need not be in contact with one another. A typical example of this process is melting ice by keeping an incandescent lamp near it. Although the lamp and the ice never touch each other, the ice melts. 

While these methods behind thermal energy generation are not visible to the human eye and can only be realized by looking at their external or physical manifestations, the examples of thermal energy are often easy to recognize as we interact with many of them. 

For instance, solar radiation heats our atmosphere, and we feel hot as a result. Similarly, there is also geothermal energy, which is intense heat flowing continuously outward from deep within the earth. The decaying of radioactive elements present in the rocks is the primary generator of this sort of heat. Then there is the seawater surface, which has a massive thermal energy storage potential due to being directly exposed to sun rays for a prolonged period. Fuel cells, too, help harness the energy produced from thermal energy.

Repurposing Thermal Energy: Efforts Across the Globe

By principle, energy converts from one form to another. Repurposing energy is, therefore, in line with our natural science principles. It is an efficient way of harnessing the true potential of energy by going beyond its immediate application. We will look at some examples of repurposed thermal energy. 

Thermal Energy Generated in Underground Car Parks to Heat Up Groundwater

A team of researchers from Martin Luther University Halle-Wittenberg (MLU), the Karlsruhe Institute of Technology, and the University of Basel conducted an in-depth study of 31 underground car parks across cities in Germany, Austria, and Switzerland.

In six of these locations, they also measured the temperature of nearby groundwater. From the heat profiles they prepared, they came to the conclusion that underground car parks consistently heat the groundwater throughout the year. It's important to note that this heat primarily emanates from the engines of parked cars.

Maximilian Noethen, an MLU geoscientist, explained, “Public underground car parks contribute more to groundwater heating than private ones, as they are often deeper and cars are parked there for shorter durations.”

The researchers also pointed out the potential for repurposing this thermal energy. For example, the annual energy output from Berlin's underground car parks, nearly 0.65 petajoules, could theoretically supply heat to approximately 14,660 households.

Repurposing the Heat of Electronic Devices

This study came from the physicists working at Martin Luther University Halle-Wittenberg (MLU) and Central South University in China. The study proposes the feasibility of using heat generated in technical devices for computing. All one needs is to combine specific materials. 

Electronic devices heat up due to the electric current flowing through them. This heat dissipates and gets lost in the process. According to Dr Jamal Berakdar, a professor of Physics at MLU, “For decades, people have been looking for ways to reuse this lost energy in electronics.” 

The new method for repurposing heat proposes the use of non-conductive magnetic strips instead of conventional electronic circuits in conjunction with normal metal spacers. “Our technology can contribute to saving energy in information technology by making good use of surplus heat,” explains Berakdar. 

Salt Batteries to Store Heat

This research piece is a recent development as the writer of the thesis, Radboud University's PhD scholar Lian Blijlevens, is about to defend her research into the usefulness of salt for heat storage. The salt in question is not the common table variety but rather types like strontium chloride. 

The core of Blijlevens' study is the salt battery, designed to store salt hydrates and water-containing salts in crystalline form. Recharging this battery involves heating the salt, which expels water from the crystals. 

“When you need the heat, you add water vapor to the crystals, and the heat is released again,” concludes Blijlevens. 

With these research papers exhibiting a thriving innovation atmosphere in this space, some solutions help repurpose thermal energy at an enterprise scale. We discuss some such solution providers in the following segments.

Energy Repurposing Solution Providers: Enterprise Scale

#1. Calefa

Calefa is a Finland-based turnkey solutions provider for the recycling of heat. Its offering includes a modular AmbiHeat heat pump plant. It utilizes ambient energy sources and retrofit systems to recycle waste heat. Since we mentioned heat pumps as a solution, it would be pertinent to briefly explain why they're considered a top option for home climate control. 

Heat pumps are multi-facility climate control devices that transfer heat from one location to another. It doesn't generate heat, only moves it, proving to be an energy-efficient choice to warm or cool a home. In the winter, these pumps extract heat from the exterior and transfer it inside. In summer, the reverse happens. 

According to data published by the organization, Calefa, in the past ten years, has delivered nearly 200 energy systems that utilize waste heat or ambient energy. It has helped save more than US$34 million in monetary terms, nearly 650,000 MWh of energy, and over 142 million kilograms of carbon dioxide in reduced emissions. 

#2. Heata

Heata, a UK-based innovative startup, came up with the idea of using heat generated by computers to offer free hot water. The startup took off as an innovation project with British Gas, to help people living in the lack of fuel or fuel poverty. 

They examined the blockchain space and got to know about the large quantities of energy Bitcoin miners were using and the similarly large volumes of waste heat they were generating in the process. To repurpose this heat, the Heata team immersed the Bitminer in mineral oil and connected it up to a radiator to test the feasibility of their idea. 

Once they found the idea executable, they brought in hot water cylinders where demand is fairly constant throughout the year. They also moved from Bitcoin mining to general computing to support the decarbonization efforts in this industry. 

Founded in 2017 and headquartered out of Godalming, Surrey, United Kingdom, Heata empowers companies to reduce their carbon footprints and saves families up to £450 per year on their energy bills. The startup closed 1 million pounds of seed funding in October this year.

Repurposing Data Centre Heat

The World Economic Forum has taken note of tech companies that are leveraging their data centers – housing their servers – to heat homes and cut carbon dioxide. Several initiatives are facilitating this process, and according to the International Data Corporation, the data center heating market could be worth US$2.5 billion by 2025. 

Stockholm Data Parks is one such initiative in Sweden that helps warm houses by harnessing the waste heat generated by Stockholm data centers. Aiming ambitiously, the initiative plans to meet 10% of Stockholm's entire heating needs this way by 2035. Echoing this potential on a larger scale, the think tank Energy Innovation notes that the largest data centers can generate more than 100 megawatts of energy, enough to power 80,000 homes.

Switch Datacenters is another Netherlands-based company that has reduced its reliance on natural gas, substituting gas generator units with data center heating. According to the company CEO, it is possible to deliver up to 97% of the server heat to homes and offices through this system. 

The Future: Global Tech Giant Microsoft Taking the Leap

Microsoft has partnered with Fortum, a Finnish company, to heat thousands of homes in Helsinki, and as the collaboration proves fruitful, Fortum expects its solution to help heat up 40% of Helsinki homes. 

Furthering their commitment to sustainability, Microsoft has now decided to power two of its new data centers in Helsinki with renewable energy, a decision projected to cut annual carbon dioxide emissions by 400,000 tonnes.

However, this environmental initiative is just one aspect of Microsoft's global influence. The company, renowned worldwide, reported US$211 billion in revenue in fiscal year 2023 and an operating income of more than US$88 billion. Microsoft's involvement in thermal energy repurposing efforts not only highlights its sustainability commitments but also lends significant visibility and adaptability to these endeavors.

Now, turning back to the first law of thermodynamics again. Energy is best leveraged when the efforts are aimed at shifting it from one form to another. Repurposing thermal energy is an efficient step towards that. There is no reason for it not to see significant growth in adoption in the coming years.