The environmentally and cost effective (older) chiller
Trevor Dann discusses the use of ThermOzone's Re-Chill concept product to address older chillers and environmental concerns
WATER CHILLERS ARE expensive pieces of equipment but are increasingly essential in today's complex buildings.
● Expensive to buy & install
● Expensive to run
● Potentially expensive to maintain
● Expensive to replace
● Expensive upon the environment
Most large water chillers will be installed as part of a design for a building or application at the construction or major refit stage. At that time the equipment choice and primary design will fall to the architect and m&e consultant. Much of their decision making will be influenced by cost and market trend - often lowest price rather than longer term quality.
Long after the building's occupants have left, those who own, lease or use the building will have to pay for the chillers and will often have little choice but to maintain them indefinitely in the absence of any new technique for cooling the building.
Presently two modes of vapour compression are dominating larger chiller production and both have their merits.
New turbo v Re-Chill screw chillers
Re-chill is a ThermOzone product allowing the customer to have a chiller rebuilt in situ, or a bespoke design to meet the site and client's needs using the most up to date technology.
A recent trend has seen dramatic improvements in operating Energy Efficiency Ratios (EERs), but more efficient machines come at a heavy price and do not suit all applications. Both the current vogue modes of vapour compression technologies, screw and turbo, knock the spots off traditional piston compression technology when it comes to energy efficiency and reliability. But the claimed energy effectiveness of new turbos may well not exceed the life cost analysis of applying screw compressors, especially when used in conjunction with older chiller frames.
When it is considered the original older chiller frame can have modern functional components applied and attuned to actual energy/cooling load requirements. Then the achievement from plant that many would simply write off becomes remarkably close to the often theoretical claims of seemingly high efficiency new chillers.
Such an approach also takes due account of known problems and limitations of an installation, reliability and usage pattern, all of which are advantageous over new plant with completely fresh unknowns, especially where specification price was the lead in the decision process.
Let's look at a cost comparison based upon actual quotations/projects. Apart from the compressor type, the major technical specifications of these chillers will be quite similar:
· Inverter variable speed drive compressors
· Air-cooled high efficiency condensers
· Modern shell and tube evaporators
· EC speed controlled condenser fans
· Modern intelligent controls package
· R134a with option (developmental) for HFOs
SEER - turbo chiller (typical) - 5.07
Re-Chill inverter screw chiller - 4.25
All the technologies described have been proven under existing Re-Chill projects.
Specifics for a 900kW Chiller with N+1 (stand by) capability
· Two off new turbo chillers installed and running - £664,000
· Two off Re-Chill (complete technical new package) - £449,000
· Initial cost of installation difference - £215,000 (in favour of Re-Chill)
Difference in Energy cost for 10 year operating period (assuming running to SEER pattern)
· Energy cost difference - £112,000 - Turbo less
· Initial Cost of installation difference - £215,000 - Re-Chill less
· Overall 10 year difference - 103,000 - Re-Chill less
Initial cost combined with 10 year energy cost and excluding likely higher maintenance costs for turbo chillers.
On many Re-Chill projects the cost of conversion may be a considerably less initial cost, as not every evaporator or condenser requires changing. For this example the chiller concerned would be functionally new under Re-Chill.
Many chillers get forgotten in time. A wall goes and up the planning authority decide to barricade the chiller. When its life is in question, the logistics become major building works, which start running into hundreds of thousands of pounds and the chiller problem has still not been fixed. Re-chill then comes into its own by giving the user a base to tackle the chiller problem and not struggle over the building issue.
It not always about energy or the environment but money and solutions to keep costs down, especially in these economically challenging times, must be a major factor, hence the practical ways of looking at costs and payback.
Other beneficial environmental factors
Other environmental benefits of Re-Chill include: reduced waste to landfill; reduced waste to indirect recycling - reducing energy of manufacture; removal of HCFCs - R22; reduced secondary effects of building disturbance; lifecycle extension - recycling by Re-Use; optimised SEER and from this actual EER in service. It will of course be noted that Re-Chill using screw compressors offers equivalent energy performance to new, also using similar screw compressors.
Actual requirements will vary from project to project. However, ThermOzone can explain what can be achieved with an old Chiller.
// The author is a director of ThermaCom / ThermOzone //
15 August 2013