Frequently Asked Questions
About District Cooling
Frequently Asked Questions
Which are the key factors for a District Cooling design
District Cooling is a very mature technology and knowledge is well spread. However it is always good to remind the main factors to consider during design:
- Proper stimulation of the cooling demand shall be performed to make the proper size of the chillers and thermal energy storage.
- The selection of the heat rejection method is also important (cooling towers, air-cooled devices, seawater or river water-cooled systems). The simulation will also be helpful to determine the most feasible solution by comparing the energy and water consumption all around the year.
- Selection of the state-of-the-art equipment: chillers with highest efficiencies, VFDs for pumps, etc.
- Proper control system with robust equipment to avoid failures and blackouts. Also, the control will be very important to make the plant work with correct efficiency and mitigate the low delta-t problems.
Is it possible to integrate a Thermal Energy Storage in District Cooling plants in operation?
Thermal energy storage is adding many benefits to District Cooling plants: peak load shaving, efficiency increase, plant reliability, and availability increase, etc. This is why most of the new DC is coming with TES.
However, some of the older plants have not TES. It is not too late to add a TES. TES can be added to retrofit DC plants in operation. In fact, in plants that are already in operation, adding a TES system will add another benefit: peak cooling capacity increases.
From a technical point of view, the critical issue is to study the hydraulics of the system. An extra pumping group might be required depending on the case. It is also important to modify the control system so the TES is integrated. Make sure you are with an experienced company.
Several actions that can boost the efficiency of your District Cooling plant
Efficiency is the key factor of a District Cooling Plant. If the efficiency is not the correct one, then all the investment will result in useless.
There are several ways to improve the efficiency of a District Cooling plant, here you can find the more direct ones:
- Make proper maintenance. Maintenance and cleaning are crucial for efficiency and correct performance.
- Retrofit your chillers. Are your chillers more than 10 years old? Chillers are in continuous enhance the process. Retrofitting the plant with new chillers may reduce your energy consumption.
- Look for integrated energy production. If you are producing cooling with chillers and heating in boilers, try to substitute this for a heat pump which produces cooling and heating with the same primary energy. Have you evaluated a tri-generation option to produce your own electricity?
- Implement thermal energy storage is best the way to boost efficiency. With thermal energy storage, part of the cooling energy production is transferred from day time (when the temperature is high and chiller efficiency is low) to night time when efficiency is higher. With TES, the overall efficiency all around the year is significantly increased.
Which are the best technologies in order to reduce the District Cooling plant footprint and built up area?
District Cooling Plant footprint is always an issue. Most of the DC plants are located in residential areas where the price per square meter is very high. A reduction in footprint is very beneficial.
The layout design and optimization are very important and good improvements have been achieved in the industry for the last years.
However certain technologies can also help to reduce the built-up area. This is the case of geothermal chillers and seawater-cooled chillers.
As these technologies do not require big cooling towers, the design of the system and much more compact reducing the footprint.
Also, no equipment is installed on the roof reducing the built-up area. These give the developers the opportunity of installing the cooling plant in the basement of any building reducing a lot the area impact.
Tips to do a proper control of the District Cooling plant
The Control system is the key component for a successful operation of the cooling plant. Therefore, District Cooling Owner should only relay on robust equipment.
It is highly recommended to make an integrated control system, incorporating not only the process equipment but also the control of the Energy Transfer Stations. By having full control of the ETSs from the plant, the operation of the system can be optimized as per the real consumption.
A fully integrated control system is also very helpful in order to mitigate Low Delta T syndrome.
Some of the owners or DCs operators would prefer even to integrate the billing system within the main control system, to avoid errors and simplify their daily work.
Why cogeneration and tri-generation are becoming so popular
Cogeneration and tri-generation systems are a successful way of integrating the production of different energy types in a single plant and in the most efficient way.
The advantage of these systems is that the amount of wasted energy is reduced to the minimum making the systems to be very efficient and respectful of the environment.
Cogeneration means the production of electricity and heat or cooling energies. Usually, a diesel or gas engine is used to produce electricity. Gas turbines can be used to.
The exhaust heat of the engine/turbine is used to produce heat or sent to an absorption chiller to produce cooling. The system is very efficient because maximizes the use of primary energy.
The concept of tri-generation is quite similar but with the production of electricity heat and cooling. In the case of using a diesel or gas engine, the heat from the engine jacket can be also recovered to maximize the system efficiency.
Is District Cooling an environmentally friendly solution?
When compared to traditional standalone chillers definitely it is mainly because of two reasons: higher efficiency and the use of environmentally friendly refrigerants.
Regarding efficiency, District Cooling has demonstrated to be a more efficient solution reducing energy consumption and therefore the carbon emissions and footprint.
Regarding the refrigerants, in the new big cooling plants, the implemented chillers are using the latest generation of Freon refrigerants (R134a, 1233zd) or even natural refrigerants like R717 or R744. Those refrigerants has really low levels of Global Warming Potential (GWP) and Ozone Depletion Potential.
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