It is a good time for facility managers to think about how to optimise building energy performance for summer – the potential benefits are not only energy consumption and capacity/demand savings but most importantly increased comfort levels for tenants too. (The most common tenant complaints in the summer are surprisingly “too cold”! This means a building’s plant and equipment is working harder than usual but still not meeting the tenant expectations).
At Buildings Alive we have put together some strategies that could assist in avoiding these complaints at the same time assist in reducing your electricity bill.
Locking out heating equipment
As we say goodbye to cold mornings, locking out electric duct heaters and boilers based on the outside air temperature can help to prevent unnecessary heating, and allow zone temperature set points to be raised. Even manual lock outs can be a good option, if the automatic controls are not well tuned. Make sure there is no overlap between the heating and cooling lockouts (e.g. boilers and/or EDHs locked out if the outside air temperature is > 19°C, chiller locked out if the outside air temperature is <17°C).
Understanding each building’s economy cycle setting
Utilising outside air can significantly help cooling down the building when it is cool outside. However, it can also make it harder to maintain good indoor conditions if it is too warm or humid. The tip here is to review the trend logs to understand how your economy cycle works.
- Single temperature lock-out: The outside air will be used if the temperature is below a certain set point.
- Return air temperature comparison: The outside air will be used if its temperature is below the return air temperature.
- Enthalpy comparison: The system uses a combined information of temperature and relative humidity to determine whether to use outside air or not
The left image below shows the OA damper was opening on a quite humid day, which resulted in an excessive use of mechanical cooling. The right image below shows the cooling usage was greatly reduced after the OA damper control was fixed.
Peak demand strategies
Peak demand does not simply occur on the “hottest days” of a year. With high overnight temperatures resulting in warmer start up conditions, there is possibility for increased morning consumption resulting in exceeding peak demand thresholds at some buildings. Monday is also more likely to have peak demand compared to other days of week because of stored heat load after a weekend.
Based on our mathematical model of the building’s most recent behaviour and up-to-date weather forecasts, we generate expected 15-minute electricity profile (green line) for the next five days and trigger a warning if the weather condition is going to be extreme. There is a good opportunity to reduce the demand costs by taking preventive actions after receiving the warnings. Here we demonstrate two successful peak demand case studies:
In first example above, peak demand time is from 7:00 to 23:00. To achieve savings, strategies such as:
- Starting the HVAC system earlier than on normal days to shift the morning energy peak, or
- Raise global zone temperature setpoint by 1°C (from 23°C to 24°C) throughout the day.
would deliver considerable savings by shifting demand and making slight adjustments to conditions.
In the second example above, peak demand time is from 13:00 to 20:00. To achieve savings, strategies such as:
- Conducting a night purge to reduce the stored heat load after hot weekend could be particularly effective on a Monday, or
- Starting the HVAC system earlier on predicted peak demand days than on normal days, or
- Raising the global zone temperature setpoint by 0.5°C, or
- Locking out one of the chillers to avoid unnecessary staging up.
would deliver considerable savings by shifting demand and making slight adjustments to conditions.
We hope these strategies provide you with some insight as to how to maintain and achieve energy efficiency savings even as summer arrives.