The question of using the services of District Cooling providers versus buying your own chillers is the subject of a seemingly never-ending debate. Indeed, this is a process that all developers go through at the initial design stage to select the cooling strategy of the property.
The Dubai property market is volatile and fluctuates up and down, depending on several market factors; and one of them is the cost of cooling. Most prospective tenants prefer “Free Chiller”, and this adds more stress to the developers to come up with a plant that is a win-win for all.
The cost of District Cooling is known, as are its pros and cons. Typically, a District Cooling scheme, as an option, eliminates installing chillers and ancillary equipment. However, it comes with connection charges, based on the total load required, as per the design of the building; demand charges, which are like the connection charges but are paid on a monthly basis at a fixed rate; consumption AED/RTH; and the Low Delta T penalty, where the landlord pays a penalty for not keeping the design Delta T.
As for CaaS, the new kid on the block, the contracts are not mature enough for us to evaluate properly. At this stage of writing this article, I must say that I am responding to the interview on CaaS that appeared in the February 2023 issue of Climate Control Middle East and, subsequently, to a presentation on the subject during the relatively recently concluded Retrofit Tech Summit, in Dubai.
The cost of CaaS can be higher than District Cooling, in the case of air-cooled chillers. This point has not been sufficiently addressed in the aforementioned interview. To enumerate…
1) There is no fixed AED/RTH
2) Scalability is limited
3) Owner must manage the plant at the end of the contract, which brings us back to Point 1; and at the 25-year mark, the owner must do the retrofitting
Meeting CHW requirements without District Cooling or CaaS
It is possible to meet chilled water requirements without opting for either District Cooling or CaaS. In the event of a project under design, it is imperative to ensure that the heat-load calculations and, later, the hydronics are done accurately and that the equipment are adequately selected to meet the required load at peak time within the industry standards, like Dubai Municipality’s green building code, ASHRAE and AHRI. Proper execution and commissioning are key aspects, as well, to guarantee the installations are functioning within the design limits. A few things to consider at this stage are…
Water cooled or air cooled
This is not an easy decision to arrive at, as both systems have their pros and cons. Generally, water-cooled systems are more efficient than air-cooled systems; however, water-cooled systems require more space, as there is a need for accommodating the centrifugal chillers, chilled water pumps and condenser pumps. They also require space on the roof for the cooling towers. Speaking of roofs, if opting for air-cooled chillers, they need to be installed there.
Water-cooled systems come at the higher initial cost, and therefore, they are best suited for large projects.
Hydronics, pumps and valves
The selection and brand choice of the pumps and valves is as crucial as the selection of chillers. Proper pump selection would avoid operational issues, such as uncontrolled Delta T, repeated leakages, high noise levels, cavitation and, obviously, high consumption.
There is no efficient plant room without controls; and by controls, I don’t only mean BMS but a way more advanced technology to control the equipment. I am referring to a chiller plant room manager with industrial controls, like SCADA capabilities, to gather data such as temperature, flow, pressure, fan speed and kWh, and mainly an AI layer, to analyse and provide the best settings in any given scenario, based on either pre-set algorithms or machine learning.
Defect Liability Management and warranty
During this period, the plant operators are required to scrutinise all the data and reports generated by the SCADA/CPM, or noticed during visual and routine inspections to identify deviations in the design parameters or installation defects, and coordinate with the contractors for rectifications. In the Defects Liability Period (DLP) is an opportunity for the plant owner’s representative to learn and get familiar with all the equipment and how to deal with the problems, as they arise or, in some cases, before they arise.
The combination of the above would eventually lead to an efficient plant room, generating just enough cooling to cope with the demand at any given time. Once such a plant is delivered, operation, maintenance and, later, retrofitting become important to run the plant for 25 years with no to minimal deviation from the design parameters.
I am highlighting key elements to keeping a plantroom as efficient as possible…
Annual Maintenance Contracts with specialists
Annual Maintenance Contracts (AMCs) shall be signed with the major equipment manufacturers’ O&M division to ensure functionality and adequate preventive maintenance is done on a periodic basis, as per the manufacturer’s guideline. This would ensure…
- Reduced equipment breakdown
- Longer asset life
- Genuine spare parts and consumables
- Best operating conditions
- Highest possible efficiency
Highly trained plant operators
A plant room consists of several equipment, which require daily and, sometimes, hourly service, especially during sandstorms for the side stream filters, which get clogged frequently, or chemical dosing systems, which may need refilling. The plant room operator would take this task and carry a routine inspection to ensure all the equipment are running properly and, if needed, coordinate with the AMC holders for their preventive or reactive maintenance visits.
Water quality and water level
Chilled water or condenser water levels and quality are crucial for a system to function properly. Dosing systems are installed to inject chemicals to maintain the water quality, to avoid coils from getting clogged and to prevent scale build-up. The pressurisation injects fresh water into the system in the event of a leakage, ensuring system pressure is constant.
Several BMS and controls providers offer analytical platforms to process all the data gathered using all the sensors and field devices that are installed in the plant room. The resultant information gives an insight on the plant condition and consumption; moreover, it predicts issues before they happen and reduces the downtime drastically.
The controls in place are integrated with a Computer Aided Facility Management software and a ticket is created for each fault, thereby ensuring a proper history on all the faults and measures taken for rectification. All this feeds to the machine learning and improves the system each day that goes by.
Retrofitting – turn the problem into an opportunity
With new technologies and manufacturers’ innovations fed by high R&D investments and fierce competition, new machines and equipment are being introduced each year, opening up possibilities of making plants more efficient than ever. The replacement of any defective equipment for any reason whatsoever shall never be like-for-like, since there is always a new equipment with higher efficiency and, therefore, a return on the investment. I call this as turning a problem into an opportunity.
No free chiller!
Some property developers provide leasing with “Free Chiller Fees”. It is an altogether different matter that there is nothing like a free chiller, since someone must pay for the energy, operation and maintenance.
When tenants are offered free chiller, that would mean there is no bill going to them every month, and therefore, most of the AC units are running constantly. This results in the below issues…
- It is difficult to maintain Delta T, which means low return temperatures.
- Tenants generally complain when they see a high chiller bill – they won’t in the case of a free chiller regime, as they don’t receive the bill; and therefore, any leaking valves are never seen and attended to, which creates significant energy losses.
- No BTU meters are installed, meaning there can be no track of energy usage and distribution.
- There is loss of revenue, and therefore, all the operations and maintenance are affected.
- It is difficult to raise capital for equipment replacement or upgrade.
As a representative of Dubai Developments, even though I do not use ESCOs for the identification of ECMs and their implementation, I do have a huge respect for companies like Taka Solutions, as I am sure they have their proven record of achievements. I do not work with ESCO as a concept, as we at Dubai Developments have achieved much higher results than any ESCO could provide to us. If they can invest in our plant and still make money it means we can do it internally. Even better, we can build the right plant and later operate in an efficient way.
The writer may be contacted at firstname.lastname@example.org.