CASE STUDY: Aircond Smart Controllers Often Underestimated As Low-Hanging Retrofit Solution
In this first case study of our “Retrofitting Energy Saving Solutions” series, we discuss one of the most underestimated energy-saving measures (ESM) and “lowest-hanging fruit” available within the portfolio of energy-saving equipment: the air conditioner Smart Controller.
This paper includes both technical and commercial aspects to cater for Facility Managers (Building Managers) and Chief Financial Officers (CFOs) who are seeking to reduce their operating expenditures (OPEX), as well as the public sector who plans for environmental building performance indices.
The general costs of energy account for 40 percent of operating expenditures. An average building accommodates at least 2 ACSUs, which have most likely operated for more than 5 years, 24 hours a day. This growing OPEX challenge is putting significant pressures on building owners and operators, prompting them to source and put into place effective efficiency measures for energy consumption.
In this case study, the client requested an energy-saving solution to be installed to reduce electricity usage. The installation of energy-saving measures (ESM) was performed at a retail convenience store with 2 units of Air-conditioner Split Unit (ACSU) operating for 24 hours daily.
Installed Digital Power Meter to measure the energy consumption pre & post-installation
Selected 2 units of 2.5HP ACSU cassette type (AC1 & AC2) only for this study.
Measurement result was monitored and recorded by both parties (STSB and client)
The temperature is set at 24°C for pre and post-installation.
14 days monitor and verification for ACSU behaviour.
24 hours of ACSU operation
TNB Tariff B category building/facilities. (Low Voltage commercial tariff)
Smart Controllers for Air Conditioning Split Units (ACSU)
To focus on ACSU consumption and energy savings, Smart Controllers play an essential role in improving the existing thermostat based control in common ACSU. The Objective of this study and the purpose of installing ESM is to demonstrate the capability of Smart Controllers to reduce the electricity consumption for the ACSU without compromising the room temperature and thermal comfort level.
Smart Controller furnishes ACSU features and control as below:
Active and intelligent compressor control
Zero loss from thermodynamic saturation
Full utilisation of cooling capacity in the cooling coil (heat exchanger)
EN60730-1 & EN60730-2-9 Certified European standard. Operating voltage 85~305 VAC. Operated with IR remote control.
A Smart controller unit is usually placed beside the ACSU (see image above). The installation required an AC technician or experienced electrician without any modifications to existing ACSU units. The process would require the ACSU power supply to be shut down between 10 to 30 minutes.
ACSU behaviour measured electrical current & indoor temperature
ACSU installed with Smart Controllers were monitored on current usage with similar conditions of operating time. Current data taken was for 1-day duration on both Bypass Mode (which means the Smart Controller is being by-passed i.e. not in operation) and Saving Mode.
The graph above illustrates ACSU operating for 24-hours in Bypass Mode, where the ACSU compressor operated for long hours without cutoff even upon reaching room temperature as per set point temperature 24°c. This operating condition of ACSU will affect the energy consumption and asset life cycle of ACSU.
The graph above illustrates ACSU operating for 24-hours in Saving Mode, where the ACSU operated with a frequent and consistent cutoff from the compressor. This frequent compressor cutoff contributed to reducing energy consumption of ACSU.
The graph below reflects temperature measurements done at the time of this study. The temperature set at 24°C for both conditions - Saving and By-Pass Mode, where the outside temperature measured was the same for both modes with sunny day conditions.
The thermal comfort within the area remained the same but consuming less energy in Saving Mode, as illustrated in the Current data.
Based on the measurement and data gathered, an average savings of 29.41kWh per day for 2 units ASCU that operated 24 hours/day was achieved, and reflected a 54% savings with Smart Controller versus baseline consumption on the existing room and ACSU.
Minimal heat load was observed to be present in the room, allowing the room to maintain the desired ambient temperature during non-peak hours. There was a slight energy waste found during peak hours where the existing ACSU was not able to perform efficiently. The Smart Controller was able to optimise the compressor duty cycle throughout the day and provides additional savings without compromising the comfort level.
The measurement data for 4th Dec is not valid since we changed smart controller setting from bypass to saving mode at 3.30pm
The duration of this energy savings case study was 4 weeks - Initial 2 weeks study for baseline data recordings (usage for ACSU in By-Pass Mode); Followed by subsequent 2 weeks with Smart Controllers in Saving Mode.
The data below shows the comparison between 2 baseline weeks (week 1 and 2) and 2 Saving Mode weeks (week 3 and 4). The resulting savings’ percentage achieved for the 2 ACSUs is 54% which is equivalent to RM209 for the 2-week period, or RM454 per month, and amounting to approx. RM5,448 per year.
Costs & Payback Period
An Energy services company (ESCO) that implements a retrofit project will typically be faced with obstacles and challenges. The solutions used to overcome the obstacles are also applicable to other similar retrofit projects.
1. Ageing Building with Ongoing Operations
Retrofitting is required to implement new energy-efficient technologies in operational ageing office buildings. However, there is a limitation on the opportunity to redesign components consisting of the building’s architectural design, façade, glazing, lighting, and HVAC system that were already in use. Retrofitting is required to implement new energy-efficient technologies in operational ageing office buildings. However, there is a limitation on the opportunity to redesign components consisting of the building’s architectural design, façade, glazing, lighting, and HVAC system that were already in use. For a successful upgrade, a solution needs to be in place for the project team to ensure continued building operations, workers productivity, and building safety while increasing staff awareness on the benefits of the retrofit.
Solution: Implement Upgrade/installation during Non-Working Hours
Rather than redesigning the whole building, the retrofit should focus on specific equipment and energy management upgrades. Air conditioning retrofit should be conducted during non-working hours and weekends to avoid inconvenience during working hours. The old and newly installed AC systems should be operated simultaneously during the transition to ensure the consistency of cooling.
2. Missing Original Drawings
The absence of original drawings of some old buildings/facilities, specifically when drawings were not kept by the building owner or drawing for electrical, were not attached to DB.
Solution: Draft new drawing for the client
Instead of expending resources trying to locate the older drawings and blueprints, the project team should prepare new drawings for the retrofit process. For example, providing new plan layout drawings for clients to get a full overview of each floor arrangement and equipment.
3. Operation & Maintenance (O&M) Post-Installation
There has been confusion on the end-user side on problems that are not related to the retrofit, where users expect the ESCO to rectify issues that are not within their scope.
Solution: O&M meeting with FM & End User
Energy services company (ESCO) should arrange a meeting with FM and end-users to identify the final list of equipment and scope under the ESCO and declare that only ESM installed under ESCO is under our O&M services during the Energy Performance contract or during the warranty period.
This pilot retrofit project demonstrates the real energy and cost savings from implementing AC Smart Controller for improving the building’s energy efficiency. The AC Smart Controllers demonstrated were able to save operating costs by lowering electricity consumption without changing the thermal comfort levels.
In summary, we conclude the following key points:
Energy savings are achievable without compromising thermal comfort: Data shows temperature reading and set points are the same at 24°Celsius for both conditions (bypass mode and saving mode). Savings achieved are up to 54% that is equal to average saving 762 kWh/month, which is an average RM 450/month.
Short payback period: The cost of implementing this AC Smart Controller is paid back within 5 to 6 months. Given the life-cycle of the Smart Controllers is approximately 5 years (of which 2 years under warranty), this is considered a good investment.
Building operations operate as usual: A key advantage of retrofitting this ESM is that business and building operations can continue to operate as usual during installation.