Warehouses vary in their operational and physical characteristics. Size, presence of heating and cooling systems, ceiling height, occupancy periods and staff levels, and presence of refrigeration are all factors that impact the energy-use-intensity of the building.
Opportunities for improving efficiency in warehouses start with sound operations and maintenance (O&M) practices. Rooftop unit (RTU) heating, ventilation and air conditioning (HVAC) systems are common in warehouses due to the openness of the heated and cooled space. Ensuring the proper function of HVAC systems is a cornerstone of good O&M practices.
The following measures and maintenance schedules should be in place as a starting point to improving building energy and water efficiency.
Table 1: Low-cost energy and water conservation measures for warehouses
|Optimize exterior light scheduling using photocell sensors
|Use photocell sensor(s) to turn exterior building lights on and off 30 to 60 minutes after sunset and before sunrise, respectively. Photocells detect sunrise and sunset accurately making them more energy-efficient than clock-based timers.
|Install LEDs in exit signs
|Since they run 24/7, install LEDs in exit signs to maximize their efficiency.
|Use an infrared camera to identify and remedy building energy leak points. As-built drawings can also help in the leakage identification process.
|Replace damaged door weatherstripping
|Especially on exterior doors, make sure that damaged weatherstripping is replaced and drafts are eliminated.
|Clean heating and cooling coils
|In the air handling unit (AHU), clean the heating and cooling exchanger’s coils and fins to maximize efficiency.
|Replace filters at the optimal schedule
|Filters should be replaced regularly, and the pressure drop in the AHU measured after replacement, and on a schedule thereafter. Too large a pressure drop caused by a dirty or improper filter can lead to inefficient processing of the air, leading to unnecessary energy usage. It can also accelerate the end-of-life of the filter.
|Temperature based HVAC lockouts to rooftop unit (RTU)
|Heating and cooling should not occur when the outdoor temperature is suitable for use in the building. Adding a temperature-based lockout to the RTU’s heating and cooling sections can ensure there is no redundant mechanical heating or cooling.
|Eliminate unneeded HVAC processes during unoccupied periods
|If the HVAC can be turned off during unoccupied periods, do it! Outside air dampers should be closed as well. Reducing runtime is one biggest “bang for your buck” opportunities to increase efficiency and reduce cost.
|Close outside air damper during unoccupied periods
|When the building is vacant, air dampers that control building ventilation can be closed to prevent any unnecessary heating and cooling on ventilated air. Ventilation adjustments should follow building best practices for maintaining air quality during Covid-19.
|Correct refrigerant charge
|In refrigerant-reliant heating and cooling systems, ensure the refrigerant charge level is at optimal levels.
|Adopt a regular HVAC schedule
|HVAC systems should be inspected and adjusted twice a year to ensure proper functioning. In cold climates, this can be done before the winter and summer seasons.
|De-lamp overlit areas
|Use a light meter to ensure the warehouse is not overlit. De-lamp areas where light power density (LPD) is high. Warehouse LPD should be about 0.45 watts per square foot per industry standards.
|Education / Training
|Employee education and training
|This measure involves energy and water conservation awareness and training for employees and building visitors as well. Empowering and engaging employees can go a long way in your efficiency improvement goals.
In addition to the O&M measures listed above, deeper retrofit opportunities exist in warehouses. These retrofit measures can drastically decrease your building’s energy use and carbon emissions.
Table 2: Deeper energy and water conservation measures for warehouses
|Install occupancy sensors
|Install occupancy sensors in transient areas such as lunchrooms and storage areas to turn lights off when vacant. This reduces energy waste from “day-burning” lights that could be intentionally or accidentally left on.
|HVAC + Electric Load
|Install variable frequency drives (VFDs) or variable speed drives (VSDs)
|Install VFDs or VSDs on HVAC fan motors and other motorized equipment when constant speeds aren’t required.
|Interior lighting retrofit
|There are different levels of lighting retrofits. A simple lighting retrofit involves light and ballast replacement with the latest LED technology. A deeper lighting retrofit is a broader lighting redesign that can include LPD and light placement optimization, daylight harvesting, and sensor controls.
|Exterior Lighting Retrofit
|Outdoor areas lit with high-intensity discharge (HID) lighting fixtures such as metal halide or high-pressure sodium (HPS) lights can be upgraded with newer, more efficient technologies such as fluorescent, induction, or LED.
In addition, the latest best practices encourage exterior lighting power density to be reduced by a minimum of 50% one hour after normal business closing and to turn off outdoor lighting within 30 minutes after sunrise.
|Install deadband thermostats and/or widen deadband zone
|Usually, temperatures within a building’s zone remain comfortable between 20.6℃ (69℉) and 23.9℃ (75℉). Installing and setting deadband thermostats can maintain occupant cover while reducing HVAC heating and cooling.
|Equipment / Plug Load
|Purchase energy-efficient tools/equipment
|When compressors, motors, and other mechanical equipment are at end-of-life, replace them with energy-efficient models.
|Equipment / Plug Load
|Purchase energy-efficient office equipment
|When electronic office equipment is at end-of-life, replace it with energy-efficient rated products.
|Reduce warehouse ceiling height
|This measure reduces the overall volume of the warehouse and reduces heating and cooling needs accordingly.
|Add roof insulation
|Roofs are a key source of energy loss. Add to, or replace the existing insulation to increase efficiency. This is most economic when the roof is due for replacement.
|Upgrading windows to the latest technology can have a meaningful impact on your building’s efficiency. When considering window replacement, additional strategies can be considered, including:
– installing a clearstory or additional windows to support a daylight harvesting lighting strategy;
– installing operable windows to help with natural cooling (when available) during warm summer months.
Heating penalties associated with these strategies should be factored in.
|Replace HVAC system with the latest technology
|Replacing the HVAC system, whether a rooftop unit (RTU) or centralized boiler/chiller system, with the latest technology, can yield significant energy savings. This is most economic at the asset’s end-of-life, but can also make economic sense beforehand.
|Automatic door closers on all exterior bays and pedestrian doors
|As an open door is an opportunity for conditioned air to escape, automatic doors reduce the amount of time service and bay doors are open.
|Install smart strips and power management software
|Install smart power strips at staff workstations to put equipment into sleep mode when appropriate. Install power management software on computers.
|Install washroom low flow faucets and toilets
|Installing low flow faucets and toilets can save water use within the building
|Install air curtains on service doors
|For service and bay doors that open frequently, an air curtain can be a high-efficiency upgrade that prevents indoor air from escaping.
|Replace electric transformer
|The electric transformer that steps-down the grid power to a level suitable for building use could be considered for replacement with more energy-efficient models. This can be discussed with your local utility.
|Investigate onsite combined heat and power (CHP) opportunities
|Depending on input fuels available in your area (natural gas, biomass, etc.), a CHP system can allow your building to produce its own heat and power, reducing energy grid reliance. Discussion with internal O&M teams is a good starting point followed by preliminary technical, economic, and regulatory analysis.
|Investigate onsite solar generation opportunities
|Depending on the solar potential in your area and the layout and solar readiness of your building, installing solar photovoltaic (PV) cells for onsite generation could help offset your reliance on grid power and the power bill. Discussion with internal O&M teams is a good starting point followed by preliminary technical, economic, and regulatory analysis.