The potential for energy savings resulting from current state-of-the-art building management systems (BMSs) is well documented. However, in order to achieve the necessary return on investment (ROI) to justify a retrofit project, the installed cost of the system must be low relative to the energy savings achieved. For small buildings (<50,000 sqft), the yearly energy usage is usually too low to justify the high installed costs of current BMSs.
The research team has demonstrated a new BMS architecture which significantly lowers total lifecycle cost to 1/2 that of state-of-the-art competitors in the small building sector, enabling ROIs that make retrofits possible through performance contracts. The results of this project clearly establish the installed costs and energy savings for a range of building sizes and heating, ventilation, and air conditioning (HVAC) configurations, demonstrating the necessary ROI to justify efficiency projects using this BMS.
The demonstrated BMS was built on a sensor and control platform which is unique compared to current state-of-the-art platforms in several ways:
- Decentralized: each device is capable of running its own high-level software, and is capable of communicating with any other device on the network. This eliminates the need for standalone controllers, which can dominate the overall cost of a BMS for small buildings.
- Low-cost: the firmware has been specifically designed and optimized to run on ultra-low cost microprocessors, drastically reducing hardware costs while significantly improving battery life.
- Class-leading wireless: a new, proprietary, low-datarate wireless protocol has been developed to specifically improve indoor range, power usage, and cost versus competing systems.
The results from the project show a 25% electricity savings and 45% gas savings were achieved in the test buildings with the retrofit BMS. Furthermore, a BMS retrofit on the entire demonstration building set was calculated to provide a 4.8 year simple payback, easily meeting the 10 year payback needed to allow this technology to be utilized in performance contracting on small buildings.
The 1993 CBECS Federal building survey estimates 45% of DoD floorspace is made up of small buildings, of which only 22% had energy management systems at the time. The demonstrated BMS technology enables the complete retrofit of these remaining small buildings using performance contracting, enabling $200 million in yearly utility savings
Several unplanned HVAC equipment outages and building occupancy changes reduced the number of test buildings for the project, however the results from the tested buildings were used to create and validate high-quality simulation models for the remaining buildings, allowing us to obtain good overall data.