ESOS and All That

Do not ignore the energy used by your Chillers

Current regulations such as ESOS (Energy Savings Opportunities Scheme) are now starting to bite for larger building users, with significant requirements to reduce energy consumption.

Reducing energy makes business sense, especially for water chillers as these are a significant load on many buildings. Yet we are seeing an increasing number of highly viable projects left on the back burner due to lack of motivation to invest in energy-saving projects, even with payback periods/return on investment consistently less than 3 years and often less than 2.

Inverter driven Screw compressor part-load efficiencies are now operating at similar levels to turbo style compressors, but without the narrow operating envelope so often restricting application of turbos. One manufacturer we work with has developed their own inverter and this has allowed them to tune the inverter and motor stator design to work in harmony and hence even more efficiently.

Screw compressors have an inherent disadvantage at very low ambient operating conditions because they have to maintain a higher discharge pressure to keep the oil flow through the compressor sufficient, but above ~ 6 – 8°C ambient we are finding this difference of little consequence. Average running conditions for most Chillers sees a typical ambient of ~ 15°C and higher than this in central London due to microclimate. However, at this average the machines are generally operating nowhere near there peak load capacity, so optimising energy-efficient operation is critical.

Design Selection of New Chillers – where is the focus?

Even now with the emphasis so much on energy costs we still see the major emphasis at the design stage is focused upon peak load capacity and Energy Efficiency Ratio (EER) at this point, and even reference to the SEER/ESEER figures do not take due account of likely real-time operating conditions.

Life expectancy & Energy efficiency at the selection stage

“… a 30% energy reduction at the chiller means 10% reduction at the energy meter for the whole building…”

Few manufacturers offer much information on life expectancy, and clearly the use and application, plus maintenance regime, is beyond their control, but much equipment is built to price, where life expectancy beyond warranty is a low marketing priority. In this regard all that glitters certainly is not gold, and for any New design we believe the starting point for any new chiller should be the 20 year marker. For our NuChill bespoke design chillers this is our starting point, with base modular designs allowing straightforward longer term repairs, and the ability to apply newer technology during the chiller’s extended life-cycle (~25 – 40 years).

The average age of chillers we tackle under our ReChill^® concept is ~ 6-8 years, and we normally only get involved where operational problems have arisen. Yet we know there are thousands of chillers in service operating reliably, but with appalling energy efficiency. This situation is not helped by the key legislative driver, Air-conditioning inspections (TM22), effectively ignoring the chillers beyond a couple of basic checks that have no impact nor follow up, yet the power cable supplying the chillers is often the largest in the building, and for most office buildings with chillers these will account for ~ 1/3 of the electrical load. So a 25% reduction at the chiller is a significant 8% reduction at the energy meter for the whole building.

Compressor Conversion & other improvement techniques for chillers in service

Even for chillers being supplied new today significant improvements can be applied, but the payback is difficult for pant already the subject of a Capital Costing assessment. So users get a cheap unreliable chiller, that uses too much energy for its first few years. The makers may work very hard to get the chiller safely past warranty, but after that the user is on his own.

So why not simply take account of the best features of chiller design at the selection stage. NuChill is bespoke, but it is not expensive for the majority of installations, and being bespoke will take account of the idiosyncrasies of the specific site for which it is designed. NuChill^® will include all current design advantages and will be engineered to last for 20 years at the optimum energy performance. Our unique Rodem^® remote access and support system.

NuChill^® & ReChill^® are the award-winning proven techniques developed by ThermOzone Ltd.

Posted in the Blog blog category on October 30, 2015.