By Admin, Boca Editorial, 12 Sept 2021
The achievement of the most energy efficient HVAC which saw a 60% reduction of electrical energy compared to replaced chiller system for buildings must be profoundly meaningful to the Sustainable Development Goal (SDG) of any society, not to mention the big electricity bill money has been saved for the building owners.
Latest project in Hong Kong has demonstrated that an innovative technology embracing Phase Change Material Thermal Energy Storage (PCM-TES) in a chiller system for buildings’ HVAC could be able to save a great load of consumed electricity by a magnificent extent. Annual energy audit report concluded that the average reduction of electricity consumption is as high as 60% and a on-site whole-system Coefficient of Performance (COP) was seen to be above 7.0, compared to around 3.0 by the replaced air-cooled chiller plant system.
It could be a game changer as the industry can now utilize and manipulate extra nearly “FREE” coolness within a chiller plant system to achieve an ultimate solution to ultra-high energy efficient HVAC system. This innovative application of PCM in chiller system has been going through a decade to achieve such a successful pilot project, thus realizing a revolutionary energy efficiency technology suffice to curtail global CO2 emission from building’s HVAC facilities significantly.
The adoption of advanced chiller plant already in the market, such as a centrifugal chiller or Variable Speed Drive (VSD) chiller, is a good ideal to reduce energy consumption. Besides the equipment, chiller plant optimization plays a vital part in the course of achieving an energy efficient HVAC system.
Coefficient Of Performance (COP) is used to describe how effective a machine works against the amount of electrical power it consumes. As for the COP of a chiller plant system, it refers to the ratio between electrical energy input in KW and refrigeration output in RT (Refrigeration Ton). The higher the value, the more energy efficient the chiller plant system is.
The COP of a single set of chiller plant could be very high, say above 10.0. However, here we are talking about the COP of a chiller plant SYSTEM in which energy input units including chillers, pumps, ductworks and tower fans as a whole. According to the COP classifications for chiller plants by ASHRAE, most of the existing chiller plants installed in the market can merely hit a COP under around 3.5.
Read the full ASHRAE 90.1-2016 chiller efficiency Classification HERE >>
Merely the employment of new VSD chillers and operation optimization could hardly achieve a top notch COP above 7.0. With the innovative application of PCM and related PCM-TES technology and its exclusive system optimization design in chiller plants engineering for energy efficient HVAC system, situation is quite different now. Industry practitioners can now try to hit a higher ceiling of COP value hardly touched before.
Phase change is the physical process when substance changes between its state of solid and liquid. Phase Change Material (PCM) refers to a special chemical compound which will release large amounts of latent heat upon freezing and absorb equal amounts of such from immediate environment upon melting during its phase change.
However, the production of PCM has been a century-old problem since its discovery in the 20th century. Despite scientists’ forlorn attempts of producing PCM of enough durability and stability for meaningful use at that time, PCM is still taken as one of the performant candidates to do the trick of storing thermal energy effectively.
Thanks to the new exquisite nanotechnology, people can now produce durable, safe and highly reliable PCM for industrial and commercial use. Today, patented PCM such as BocaPCM has become a series product, covering different phase change temperatures ranging from -100℃ to 1100℃, dedicate for various kinds of heating and cooling applications.
When it comes to green energy strategy, renewable energy is just one side of the coin, the other side is engraved with the chosen names of the new technology capable of effectively storing energy. PCM in chiller system is one of them.
With PCM, people can effectively store latent heat in form of heat or “coolth” and release them for use whenever needed. This mechanism is called “Thermal Energy Storage” (TES), or PCM-TES as PCM is themed.
Like a Lithium battery which stores electric power, PCM acts like a thermal battery which can store and release thermal energy in the form of heat or coolness.
In practical use, a typical PCM-TES comprises of a big thermal tank for the accommodation of hundreds pieces of panels filled with PCM. This is the place where the mechanism of TES will take place.
Incorporate PCM-TES technology into chiller plant system in 2017, a signature invention: the Ultra High Efficiency BocaPCM-TES Hybrid Power Chiller Plant System by Boca, laid a milestone in the industry as it is able to reduce 60% or even more of the electricity consumed by existing HVAC facilities in buildings. This prodigious energy-saving level dwarfs any other existing solutions for energy efficient HVAC system.
In this system, PCM-TES can be imagined as an “ice bank” in which a thermal tank is employed to accommodate hundreds of panels filled with frozen PCM. Like how you make ice cubes out of your home freezer to cool a glass of Coke, not only buffering, these frozen PCM panels are the source of additional free ‘coolth’ which helps cool the flowing water in a chiller plant system when generating refrigeration tons for central air-conditioning purpose.
In fact, there is another kind of TES already prevailing in the market, the Ice-TES or Ice-based TES, ITES. Ice-TES uses water instead of PCM as the liquid medium for phase-changing (frozen) into solid state.
In practice, the benefit of using Ice-TES is that it can decrease electricity costs by shifting electric energy consumption from higher-priced peak rates to less-costly off-peak (predominantly nighttime) rates. However, as an energy efficient HVAC system solution, using PCM in chiller system is head and shoulder above Ice-TES in terms of its real-deal saving capacity of both electricity and related bill money.
Save electricity Money?
Claim to reduce 1/3 central air conditioning running cost only because of lower tariff rate during off-peak hours at night.
Reduce 2/3 central air conditioning running cost because of lower tariff rate during off-peak and most importantly, higher efficiency all the time.
Consume 100% more electricity during charging at night due to very low freezing temperature at -5℃.
PCM freezes at 8℃, whole system consume 40 - 60%+ less electricity for all the running time.
Save the environment?
Hardly ever! It has nothing to do with energy saving.
Sure! Help reduce a significant amount of CO2 emission.
See the full comparison HERE>>
Whether the ice-based TES represents a sustainable solution or not has been a controversial issue along its proliferation. A study conducted by Nova University in 2010 found very few energy benefits on very limited conditions from base – only two installations. In principle, from from the angle of theory and common practice, Ice-TES is not a real-deal green solution like the use of PCM in chiller system that help reduce electricity consumption and CO2 emission.
While water with impurities solidifies well below zero ℃, the freezing point of the PCM used in the system magically nailed at 8℃, meaning far less electrical energy will be spent in phase-changing the liquid into iced cubes.
Unlike Ice-TES, the PCM-TES tank equipped in this energy saving chiller system in HVAC not only plays as a “coolth” buffer. Because the chilled water flowing in the pipes of a chiller system is cold enough to freeze the PCM panels inside the tank, these extra “coolth” from the frozen PCM panels are nearly free rider product from the chilled water. In simple words, a 8℃ instead of a below-zero ℃ freezing point spends far less energy for the phase change process, this benefits the new energy efficient HVAC system.
Namely, the addition of PCM-TES tanks alone can be able to help save about 15-20% more electrical energy. Higher energy saving level results from the use of new type VSD chillers. But most importantly, in real practice these PCM-TES tanks make sophisticated and powerful chiller plant optimization measures such as serial chillers design and high Delta strategy possible and run perfectly.
This new PCM-TES chiller plant system technology has seen a COP higher than 7.0 from pilot projects, making it very likely the most energy saving chiller plant system in HVAC we can find in the market. You may discover some successful projects of this new PCM-TES technology in Hong Kong, US and Europe.
Future development includes the improvement of system optimization efforts such as involving artificial intelligence to control and regulate chillers’ daily operation. Boca, the inventor of this new PCM-TES package is finishing an new add-on design to exiting chiller plants system without replacing the whole system. This ask for a new PCM with critical phase change temperature fitting for this purpose.
New green technology casts a promising future for our lovely healthy planet. However, innovation takes time to go through its innovation diffusion curve. In this course, education, promotion and the support from government as well as facility owners are vital to the proliferation of this new awe-inspiring green technology. In nearest future, PCM-TES will become a new typical element of any green chiller plant for most energy efficient HVAC system in buildings.
To learn even more of this new energy efficient HVAC system technology, click for the whole story at the official website of Boca: pcm-tes.com