Title: Advanced Controls for improved energy efficiency of chillers
In the non-domestic sector, cooling requirements are high, DECC published paper (Energy Consumption in the United Kingdom - http://www.decc.gov.uk/assets/decc/11/stats/publications/energy-consumption/2327-factsheet-industrial-energy-consumption.pdf) and (http://www.decc.gov.uk/assets/decc/11/stats/publications/energy-consumption/2326-factsheet-service-sector-energy-consumpt.pdf) highlights in 2009, 2% of total energy consumed in industrial sector for refrigeration purposes and 5% for cooling and ventilation in the Service Sector (of which 21% is retail sub sector), this indicates the scale of market potential in the United Kingdom; chillers are the primary source used to satisfy this cooling need for a wide variety of purposes, such as air conditioning, controlled cooling of products and machinery, food preservation and many more.
To increase chillers efficiency, different energy conservation measures have focused on different elements of chillers, for example inverter on condenser fans or compressors, Floating Head Pressure regulation (FHP), liquid pump amplification, defrosting optimisation; these improvements have already been made by manufacturers and refrigeration specialists. The most wide-spread control technology is PID (Proportional Integral Derivative), a closed-loop regulation that drives a process input (valve, motor speed) when a difference between measured and setting value is observed. The shortcoming of PID is that it becomes unstable when its tuning parameters are not chosen correctly, which is frequently the case as process or building needs depend upon production constraints and environmental conditions; thus, we predict that 80% of the PID loops encountered on sites are badly tuned. As a consequence, PID generates oscillations that degrade the operational performance and energy efficiency of the chillers and lead to premature ageing resulting in high maintenance costs and shorten life span of the product.
On the contrary, a new control technology uses a physical model; this improves the efficiency, reliability, stability and the responsiveness of the chillers. As a consequence, less energy is consumed, furthermore indirect energy savings are generated; as the system is well-regulated and energy efficiency measures (FHP, electronic variable motors) can be safely implemented. This type of control is robust and easy to implement and maintain.
The new control technology has been through comprehensive R&D at an R&D centre on a prototype in a working environment. Its benefits in comparison with a classical PID control have been demonstrated; replacing PID by new control technology led to 12% energy savings and the combination of the new control technology with FHP led to 40% of energy savings, of which 20% could be attributed to advanced control. This technology is currently at TRL 6 stage, the goal of the demonstration project is to reach TRL8 by the end of the project, next steps are to integrate the new control technology into a chillers pack and carry out functional testing by implementing and monitoring the chillers pack on site.
Despite the impressive results from R&D, the new control technology development encounters difficulties as chillers manufacturers are not specialised in controls and end users are not so keen to take the risk to experiment innovation.
This project proposes to demonstrate the new control technology applied on chillers to make them energy efficient in comparison to existing energy footprint; it is an innovative type of control that generates energy savings, we propose to conduct a building scale demonstration of the new control technology undertaken with a leading integrator of chillers pack (at the heart of the supply chain) and a national superstore chain (where chillers represent 50% of the total energy consumption). This partnership will demonstrate quantifiable evidence of chillers energy efficiencies, mitigating risk of new technology and its implementation, whilst highlighting the potential for mass market roll out through this supply chain.