the process of converting unused waste energy into other forms of usable energy.
Details of Recovered Energy
Electric energy doesn't simply vanish into thin air. It converted to other kinds of energy, which happens at a molecular level, obscured from our naked eyes. In fact, we learn from the first law of thermodynamics that energy can't be created or destroyed, only conserved. Your smartphone's battery decreases as you use it because the circuit consumes the energy inside to power the screen, respond to your input, create sound, and generate heat due to slight inefficiencies.
To understand the concept of recovered energy, we first have to establish a point of view: us.
Humans are the only species intelligent enough to grasp how energy works and utilize it to make our lives easier. Electricity is our primary source of energy. We produce electric energy from the sun’s heat, energy through solar panels, kinetic energy through hydropower plants, and weak nuclear bond energy through nuclear power plants. We use electric energy to manufacture products we use like food, tools, and vehicles.
The byproduct of these manufacturing processes comes in many forms, including heat energy from electrical machines, chemical energy from chemical waste, even radioactive energy from leftover nuclear fission fuels. The recovered energy is what we produce through the process of converting these unused energies. We can store the unused energy to power other machines or convert it to other energy forms. The benefit of this process is highly impactful, especially since we remove the potential danger of excessive waste while using it to make our lives easier and more efficient.
Example of Recovered Energy
A small yet widely available and easily observed example lies within an electric car. Traditionally, a car reduces its speed by grinding a brake pad on a rotor that's attached to its wheels. In an electric car, instead of pressing the brake pedal to slow down the vehicle, you can release the throttle pedal. This will let the car slow down by itself due to the combination of the vehicle weight, the inertia of the wheels, and friction between the tires and the road. When you release the throttle pedal, the motor instantly turns into a generator, feeding off of the wheels’ rotation. This generator produces a small amount of electricity and stores it in the car’s battery.
On a much bigger scale, we can look at the High-Temperature Borehole Storage System (HT-BTES) system at the Xylem Water Solutions Foundry AB. Located in Emmaboda, Sweden, the foundry melts steel and casts it to make water taps, steel pipes, water valves, and other water appliances. Wasted heat energy from the manufacturing process is abundant. So, they store it inside a borehole and use it in winter to warm the nearby residential area, power a sauna, or boil water.
The heat from machines like foundries, ovens, compressors, and even Uninterruptible Power Supplies are harvested using specialized water. Then, they're sent to the HT-BTES system. This system consists of 140 boreholes, with 4 meters of spacing and a maximum depth of 150 meters. A thick coaxial plastic tube is inserted into the hole to store the heated water. The water is mixed with special chemicals that prevent it from rusting the steel pipes and storing more heat energy. In 2015, the HT-BTES system harvested 3600 MWh (Mega Watt hours) of wasted heat energy and utilized 2600 MWh of heat energy to power the nearby residential area.
Significance of Recovered Energy
The concept of recovered energy aims to convert wasted energy into other energy forms. Energy neutrality is the ratio of the amount of input energy and output energy — an essential factor in the conversion process. As we progress into the globalization era, the energy neutrality calculation is becoming more critical for our economy and the safety of our planet.
For example, creating one liter of biofuel from one liter of corn is considered an energy negative process. It's called this because one liter of corn has a total energy of 7670 Wh, while the end product of one liter of biofuel has a total energy of 5962 Wh. That’s a loss of 1708 Wh of energy, which equates to -22.3% of energy loss. This negative number is not viable for economic and planet sustainability.
An energy positive process is good for the economy because it means that the final product has more energy, raising its actual value. Or, in the HT-BTES system's case, it completely removes the need to pay for an extra heating system in the winter. You could put that saved money towards a higher living standard, improving the country’s economy. Recovered energy seeks to boost the energy neutrality equation to those positive levels.