CUTTING ENERGY USE INTELLIGENT CONTROLS
There has been a major shift in the expectation of clients so that, even in temperate climates, cooling is de rigueur for bedrooms
a modern-day equivalent of the ‘intelligent site engineer’. It provides a form of system control capable of adapting operation so that mechanical services operate at best efficiencies, or using lowest utility charges while also looking to the future to predict the opportunities for enhancing operation. This can draw on data from hotel booking systems, internet weather forecasting and even spot pricing from utility companies combined with historical databases of building operation and response. There has been a major shift in the expectations of clients so that, even in temperate climates such as the UK, cooling is virtually de rigueur for bedrooms. It’s also frequently essential for more densely occupied meeting rooms, conference facilities and restaurant areas. These two quite separate applications
can produce complex cooling plant schedules. The cooling for bedrooms will typically use terminal units (potentially with associated centralised ventilation air) with operation varying according to guest occupation. Meeting and conference areas are likely
to have dedicated air-handling units whose predominant load is linked directly with client events. The complexity of demand is being matched by the ingenuity of the engineering community, with the development of control algorithms and sensing techniques that can lessen the carbon footprint by reducing primary energy use. This technology is increasingly available
from major chiller manufacturers and, importantly, becoming more available for retrofitting existing installations as in the example below.
How retrofitting Smartcool improves energy efficiency 12°C
Conventional compressor operation Conventional fixed control band
10°C 7.5°C 5°C Time
C set point. At the top of the band, compressor output is at its maximum. As temperature is reduced, the plant is off-cycled until the bottom of the band is reached
Fig. 1 – Illustrating a proportional control band with a 7.5o
12°C 10°C 7.5°C 5°C Time
Fig. 2 – Illustrates the same control band with Smartcool installed. By intelligently predicting the load pattern in the second cycle, the plant is unloaded earlier in the first cycle to achieve an energy reduction
Compressor operation with Smartcool OFF Compressor operation with Smartcool ON Conventional fixed control band
Compressor operation with Smartcool OFF Compressor operation with Smartcool ON
12°C 10°C 7.5°C 5°C Time
Fig.3 – By overlaying the upper and lower limits, the effect that Smartcool has on the control band becomes clear. The lower band limit can be raised and the top either raised or lowered to achieve a net reduction of energy
Conventional fixed control band Smartcool dynamic control band
22
CIBSE Journal October 2012
www.cibsejournal.com
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