Today, the reduction of emissions by the heating and cooling sector is a critical factor in mitigating climate change and reducing air pollution.
Traditionally, heating systems have been designed to use high temperatures, mainly due to the high demand for heat from buildings, which were built with poor insulation. In order to achieve the high temperatures (60-80oC) necessary to heat these buildings, in most cases, fossil fuels were “neededed”.
Technological innovation, more demanding regulations and current trends towards more energy-efficient buildings can allow a broader development of clean energy technologies, such as solar thermal energy, aerothermal, hydrothermal energy or low-temperature geothermal energy, as well as waste heat sources.
These sources are widely available in many regions, but until now they were not used because they were low enthalpy energy sources that can only be used in the form of heat and cannot be transformed into other types of energy.
This type of energy does not allow, for example, efficient electrical production, or its industrial use in very high temperature processes. However, this energy is easily usable for use in heating and cooling. So why not take advantage of it in these applications, avoiding wasting other types of energy?
How do I use this low-enthalpy energy efficiently?
To analyze this point, it is advisable to review a little basic thermodynamics. Thermodynamics studies the relationships between heat, temperature and energy.
Heat flows naturally from a warmer focus to a colder one, for example, if I have a very hot cup of tea (Hot spotlight), and, some ice cubes (cold focus), as soon as I put them in contact, the heat will flow from the tea to the ice, melting it within a few minutes. Immediately we observe that, at the end of this process, we have the two objects (focuss, to call them in a more technical way, but after all, the cup of tea and ice), at the same temperature, intermediate between hot (tea) and cold (ice) temperatures. Tea has given some of its heat to the ice by melting it.
But… Can we achieve the opposite effect? That is, is there any way to “transfer heat” from tea to ice, to make the tea even hotter and the ice even colder? A priori, it doesn’t seem very natural, but the answer is yes, there is a technology, called “heat pump” that allows heat to be transferred from a cold bulb to a hot bulb, consisting of a “small consumption of electrical energy“.
Yes, but… how “small” is that consumption? Well, it depends, above all, on the temperature difference between the two sources. The smaller that difference, the smaller the electricity consumption. For example: it would cost me more electricity (and, consequently, more euros) to transfer that heat from ice to very hot tea, than if I simply wanted to transfer it from a glass of cold water to a glass of warm water, because, in the latter
In this case, the temperature of both objects or spotlights is closer.
The heat pump, key to energy savings
At this point, you may be imagining that a “heat pump” is something strange, but it is a device that does not require much knowledge for its use, or great maintenance… in fact, almost all of us have one at home, the fridge.
In the fridge, we managed to reduce the temperature of a cold fireplace (The inside of the fridge) and transfer that heat to a hot bulb (The back rack of the fridge), consists of an electrical consumption, which is greater the colder we want the interior, and the less heat the grille dissipates (the less ventilated or the temperature of the house is, etc.).
Another fact: The heat pump, as such, the oldest in operation is located in the City Hall of Zurich and has been operating since 1937 providing heating by taking advantage of the waters of the Limmat River, so it does not seem a very new technology!
Okay, it’s simple, but then it’s not renewable energy… consume electricity! Yes, that is true, but the proportion of electrical energy it consumes is lower than that of other systems. The main advantage of these equipment is their high performance, which we call COP.
For example, a machine with a COP=4 allows you to take advantage of 3 units of “low enthalpy” clean energy (For example, 3 kWh of energy contained in the ambient air), using only 1 unit (1kWh) of electrical energy to produce, in total, 4 units (4 kWh) of energy for the heating of the house. That is, with 1kWh of electricity I get 4 kWh of heating, that is, “I have saved 3 kWh compared to a conventional system.” !75% energy savings!
In addition, this allows us to make better use of what we call the “hybridization” of renewables. What does this mean? Well, if we had to get all that energy for heating, for example, from a solar photovoltaic system, we would need a large area of solar panels, which would entail a high investment. However, taking advantage of heat pump technology, we only need to install 25% of the solar panels, the other 75% we are going to extract it, for example, from the air or from those other energies that we have called “low quality”. In this way, we have reduced our renewable electricity installation to a quarter. And we already have “100% renewable energy“!
And what does Sunthalpy do?
As you can imagine, the performance of the heat pump is key, since it is what marks what percentage of electricity we need and what percentage of “low quality” energy we can take advantage of. And we had said that it is much better the closer the temperature of the cold bulb (that “low quality energy”) and that of the hot bulb (“building that we want to heat”). But… How do we get those temperatures closer?
In Sunthalpy we approach the problem from both sides.
On the one hand, we want to reduce the temperature that is necessary to heat a building. In that sense, efficiency is maximized if we isolate the house as much as possible and replace conventional radiators with more efficient heating systems.
To give us an idea, a conventional radiator works at temperatures between 60 and 75oC, a low temperature radiator can work around 50oC, air systems (fan coils) normally used in offices or commercial buildings work at between 40 and 50oC, and underfloor heating systems do not need temperatures above 35oC.
In our case, Sunthalpy promotes heating systems that use walls and underfloor heating, with its own patented technology, which allow you to heat buildings in a much more efficient way, at a very low temperature (even below 25oC), with levels of interior comfort higher than conventional ones.
In addition, going one step further, Sunthalpy uses energy storage systems to maximize production in the periods with the best performance, integrated into the home itself. A heat storage tank occupies a “useless” space, why not turn it into a pool? Or use the housing’s own structural concrete to store that heat? That’s the idea to be “the most efficient.”
On the other hand, we take care of looking for that “low quality energy” that best fits in each case to maximize performance.
As an example, the Sunthalpanel panels Allow you to take advantage of the incident solar energy by combining photovoltaic production, which will serve to supply electricity to the house and the heat pump, so that it is 100% renewable, and, at the same time, the thermal energy of the Sun, even on the days of lower radiation or when it rains, making it that “low quality energy” that we need to put the heat pump to work with average seasonal yields that can be greater than 6 (remember the recipe: one unit of electrical energy per 5 units of “low quality” thermal energy).
But not only the direct energy provided by the Sun is usable. For example, we can extract that thermal energy from the waters of a river, sea or lake (hydrothermy), from the energy accumulated in the ambient air (aerothermal) or in the first meters of the earth’s surface (geothermal).
Low enthalpy energy in the world
Another fact that helps us get an idea of the enormous available thermal potential that we are not yet taking advantage of: Paris has an annual final energy consumption for heating residential buildings of approximately 8,300 GWh/year. Considering a flow of the Seine River of approximately 500 m3/s, if we took advantage of 1oC of the thermal energy of the waters, we would have a “low enthalpy” thermal energy of approximately 18,335 GWh/year, that is, more than double the total heating consumption of the residential sector of Paris. A Paris without chimneys doesn’t seem so complicated.
But not only rivers have a high potential, the sea is another storage of energy. Little explored, even in the most adverse climates! One of the largest projects worldwide that uses heat pump systems with exchange of energy with sea water, is located in Norway, in the city of Drammen. It is a heat network with a power of 15 MW (More than 50,000 inhabitants supplied), which uses water from Oslo Fjord, with a stable temperature of 8-9oC throughout the year, achieving a COP greater than 3. And it’s Norway!
And speaking of cold places, in Finland we find the largest heat pump facility in the world, which supplies the entire neighborhood of Katri Vala, in Helsinki, taking advantage of heat from the city’s wastewater. Waste also has a thermal value!
We see that even in the most extreme climates it is possible to take advantage of this “low enthalpy energy.” In the countries of northern Europe you already know it, in Canada they have been using it for many years… and why hasn’t it been done here, with much more favorable conditions? Probably that’s why, because of our most favorable climate… the heating season was shorter and less intense, and no one seemed to care about reducing consumption. But, do we stand idly by? Or do we start the change?
Good for the environment, good for the pocket!
_ article written by Belén Garzón