Free cooling can improve some measures of efficiency, but tropical countries may be better off looking at where their power comes from
The importance of data centers to the average citizen should not be underestimated. They are vital for even the most common daily function – from a simple internet search to a bank transaction. Their importance can even extend to, for example, the monitoring of the electricity delivered to one’s home.
But data centers are accused of being environmental villains due to their exorbitant consumption of energy, so reducing their environmental impact is vital. In this context, photovoltaic generation is an interesting alternative to free cooling, and especially suitable for tropical regions such as Brazil.
Using the wrong metric
Ecological footprint (ecofootprint), according to WWF Global, is connected to the impact of human activities, measured according to the production area and the amount of water needed to produce goods and assimilate the waste produced.
Data center efficiency is usually rated by PUE, a parameter conceptualized by the US, the EU and Japan to establish a single metric to assess the energy efficiency of data centers. The concept is not new, because the relationship between useful energy and invested energy is used in many other processes.
The calculation of this indicator is based on the relationship between the energy consumption by the installation as a whole (total energy) and the energy consumption exclusively by IT equipment (IT energy). Like any indicator, PUE may be called into question, but it remains a useful metric nonetheless.
It did not take long for the cooling system to be considered the greatest enemy of PUE; as a consequence, its efficiency has become closely related to its reduction. There is nothing more tempting than getting something for free; for instance, a data center that could potentially be cooled by nothing more than the forces of nature. Since this is not possible, the solution is to decrease a good percentage of energy consumed by central chilled water, taking advantage of free cooling, thus decreasing PUE.
The largest data centers in the world are located in the northern hemisphere, which is not surprising since this is where the largest manufacturers of infrastructure equipment are located. So it is natural that the research and development centers of these manufacturers develop solutions that meet the climatic conditions of the hemisphere in which they operate. Any solution adopting free cooling as a way to optimize data center cooling will be much more effective the farther away from the equator, where the average annual temperatures are lower.
Any solution adopting free cooling to optimize a data center will be more effective farther away from the equator
However, the crucial aim of business is financial success, and this has led manufacturers and their sales departments to market these solutions as ideal ways to decrease PUE, regardless of their geographical position in the world. As a result, some engineers have done a real juggling act to justify the cost of acquisition and implementation of free cooling systems in countries with tropical climates – including Brazil.
Why not go solar?
Photovoltaic power generation is the conversion of sunlight energy into electricity using modules made of photovoltaic cells, which are mostly manufactured using silicon. The photovoltaic modules can be installed on top of a data center, with the advantage of helping reduce the thermal load on the building, since the shade caused by the modules reduces heat absorption, which would have been transferred to the internal environment.
Another important component of the photovoltaic generation system is the inverter. This equipment is responsible for transforming the direct current created by photovoltaic modules into alternating current. The output of these devices will be connected to the energy provider, and for this reason the inverters are also responsible for synchronizing the the wave of alternating current generation system and the ripple current from the external grid.
Simultaneously, the inverters have an anti-islanding protection, which disconnects the generating system from the energy provider when the inverter identifies changes above predetermined voltage and frequency values in the grid. Another extremely important function of the inverters is tracking the maximum power point (MPP) of the photovoltaic generator that varies according to variations in solar irradiance and its operating temperature. The inverter must accompany the variation from this point in order to make the best use of the photovoltaic modules.
Free energy, not free cooling
The concept of free energy emerges as an alternative to free cooling, on the grounds that it is more suitable to the Brazilian reality and to other countries with similar weather. It is related to power generation using any renewable energy source that has been obtained directly from nature through an environmentally sustainable process. This solution, as well as free cooling, aims to improve data center effectiveness and reduce the ecofootprint from data centers in general. Because of the distributed generation and the ability of interaction between the minigeneration and the energy provider, free energy has become a feasible concept.
Taking photovoltaic power as an example of free energy, when data centers are transformed into generation plants, they may apply this energy to the grid and offset it – not only from an energy standpoint but also economic. Once the concept of free energy is settled, it is inserted into another new term – EcoPUE – bringing a new idea for calculating PUE that is now even more environmentally friendly and presents a sustainable aspect, where the reduction of energy consumption in the data center is linked to the subtraction of the energy generated by the photovoltaic generation system. This renewable generated energy is called ‘free energy.’
Use what works
The increased demand for processing and storage of data, together with the environmental problems caused by high energy consumption, are forcing data centers in Brazil, and elsewhere, to seek more technological solutions and become increasingly green, using energy more efficiently and sustainably while providing a quality service to customers. A combination of existing technology and techniques, along with new government legislation in Brazil, are now in place, so significant improvements have already been achieved. As an alternative to free cooling, the use of photovoltaics is increasingly being seen as a viable option in countries with a high solar radiation index – like Brazil – where renewable energy can be obtained for free from the natural resources available on the planet.
The concept of EcoPUE demonstrates that greater efficiency from a data center can be enforced with the use of photovoltaic generation, thus reducing their environmental footprint.
Paulo Cesar de Resende Pereira is director of Fox Engenharia e Consultoria in Brazil
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