Energy efficiency – Sustainable Energy – TU Delft


Welcome back guys! You can imagine that an increase in energy efficiency will allow us to conduct the same amount of activities, or even more, at a lower energy use. This can help to curtail our emissions, while increasing the profits. Remember that the energy efficiency can be described as the percentage-ratio between the energy output, and the energy input. However, for many activities the energy output is less relevant. For example, for transport, the heat generated by the combustion engine is not relevant. Here we are rather interested in the actual function of the car, transporting you from A to B. In this case the energy efficiency can be defined as the number of kilometers driven per liter of fuel, so distance driven divided by the fuel used. It is very relevant to know how efficient a piece of equipment, a company or a sector is, for instance if we want to compare these.

For this purpose, we can take the inverse of the energy efficiency. This we call the specific energy consumption or SEC. The SEC is the energy input divided by the activity output, such as the distance covered by a car. Subsequently, you get for instance Joule per kilometer or liter per kilometer as unit for the SEC of a car. With the current knowledge on what energy efficiency is and that energy is required for all human activities, it can be stated that a common objective is to strive for energy efficiency improvement. This means that we want to increase the amount of activity per unit of energy input. Simply said this is reached by reducing the amount of energy required per unit of activity. Good news is that throughout the history of mankind, the energy efficiency has been improving in an autonomous way. I would like to describe this with an example, the example of illumination. A candle, used for purposes of illumination for more than 5000 years, has a light production of less than 1 lumen per Watt. Lumen is a unit for the amount of visible light emitted by a light source.

The incandescent lamp, which was already a huge improvement on the candle, produces up to 18 lumens per watt of power. Led lighting which is now gaining ground, can produce 120 lumens per watt and that number is expected to further improve. In this graph you can see that the overall improvement has been immense. Very significant energy efficiency improvements have been identified for basically all of human activities. Nevertheless, there is still a lot to improve. We need to continue the improvement, but how can we do that? To start, we don’t have to look far for these improvements. Every day we are paying too much for energy, due to among others poor insulation and inefficient lights, appliances, and heating and cooling equipment. This is money we could save by investing in energy efficiency for our homes. In our homes especially insulation can strongly contribute towards energy savings regarding heating and cooling. Additionally, heat pumps can contribute to heating and cooling efficiency. By extracting heat from a low temperature heat source, such as the environment, and delivering it at a higher temperature level, the energy input for heating can significantly be decreased.

During summer energy used for cooling can also be saved by reversing the process. The next step is to acquire state of the art appliances with the latest energy labels. For instance, energy efficient fridges, televisions and laundry machines are a must. Together with efficient lighting the energy savings in our homes can be significant. The same measures can also lead to great savings in for instance schools, hospitals and office buildings. Just like for our homes and buildings, the energy efficiency possibilities for the industry are very diverse. A nice example is the state of the art research being conducted at Delft University of Technology to increase process efficiency by means of the “perfect reactor”. The aim is to have complete control over chemical reactions at a molecular level, in order to ultimately realize fully sustainable, waste-free and thermodynamically efficient processes. If successful, this will lead to industrial processes which consume way less energy and resources per unit of product.

These type of efforts are in the field we call process intensification. Heat pumps can also have Industrial applications, to upgrade waste heat to a useful temperature. In addition, process integration is increasingly applied in industrial clusters or complexes to reduce the energy use. Within a company the waste heat of one process can be used as input for another process. But it can also be applied beyond company borders. For example, in an industrial complex, steam consumers can acquire steam from other parties with a surplus of steam or for whom steam is a rest product. Think about a waste incinerator supplying steam to nearby chemical plants. Through this process the total heat exchange system is minimalized for energy use. The steam consumers do not have to generate their own steam anymore which is traditionally carried out with natural gas or oil-fired boilers, hence fuel is saved. In general, process related technology which improve the efficiency of the fuel to power conversion and the power to motion conversion are required to increase the efficiency even further. For instance, we can implement more efficient boilers, furnaces, engines, pumps etc.

Simultaneously, we should optimize the use of these components to get the most out of their potential for an increased efficiency. We now covered the residential and industrial sector, but what can we do for the transport sector? For transportation, energy efficiency can first of all be improved by reducing friction. This can be realized through improved aerodynamics of the vehicle structure. Take a look at this aerodynamic car developed at TU Delft, called the Ecorunner. With the Ecorunner 5, a distance of nearly 3,700 kilometres could be realized on an amount of hydrogen equivalent to 1 litre of petrol. The team aims to even better next years! I hope you have now gained some insights in how we can further improve our energy efficiency over all sectors. I invite you to be creative and think along how these measures could be applied in your home and country, and possibly what other measures are possible. Who knows, maybe you have the million-dollar idea!.