Why Building Automation is Not as Smart as You Think
En son güncellendiği tarih: 23 May 2019
Building operations and sustainability departments are increasingly under pressure to contribute to assets’ bottom line through cost savings. As real estate companies look to trim their budgets wherever possible, so continues scrutiny of building operations dollars.
And yet, there persists an assumption that automation through the Building Management System (BMS) will lead to “smart” buildings and improved performance.
It is true that a building with a properly programmed BMS will run more efficiently and have a healthier indoor environment than a building without any controls. However, the programming and adjustment of these systems still depend on persistent diligence of a human operator. An operator — quite frankly — who actually enjoys learning about and tweaking their BMS — a rare quality to be found in any human being.
The ability for equipment to be turned on ramped up, or ramped down automatically based on specific set points allows for a response to conditions that no human could operate manually at scale. Obviously, there is tremendous value in a BMS and it can be an invaluable tool to reduce costs.
On the other hand, the Department of Energy found that improperly configured building management systems result in 20% of building energy usage. For a system that costs around $2.30 per square foot to implement, the costs associated with non-optimal automation can negate any improvements in building performance.
What's Your Schedule?
Setting and executing equipment schedules are basic functions of a BMS, but mistakes are made surprisingly often.
If schedules were always wrong, it would be an easy problem to solve — simply get rid of schedules. The issue is that an operator does not know a schedule is off unless they check or unless a tenant complains, and each schedule may drift away from prescribed set-points over time as seasons and/or occupancy patterns change.
This is the risk of completely depending on automation without a method to verify effectiveness (a problem not limited to the BMS, it is inherent to all software-based automation, as The Atlantic recently wrote about). Schedules may accidentally be changed when maintenance needs to be performed and schedules or set points never changed back to original settings. Additionally, operators may sometimes be unnecessarily conservative to ensure that tenants remain comfortable, such as when setting wider temperature bands and extending startup and shutdown hours.
It would be surprising to find a real estate portfolio without any scheduling issues, despite the significant dollars wasted as a result. In the example below, changing the lighting schedule from nearly always on (represented by the grey line) to reflect real occupancy hours (represented by the blue line) saved one commercial building 57% of their lighting costs, or $24,000 a year.
Clearly, in this case, automation did not guarantee efficient operations as an intelligent system should otherwise be able to achieve.
Making the Right Adjustments
BMS installation includes a process of tuning (commissioning) the system to the maximum efficiency for conditions at the time of installation. However, there is generally no mechanism to account for the changes that building experiences over time. Tenants, building staff, climate, and maintenance needs all change over the lifetime of a building. So while optimization at installation is important (and difficult — just ask any building operator), ongoing optimization is equally, if not more important.
A key problem lies in tracking the adjustments. If a set-point is changed, there’s usually no record of that change. Ideally, there would be a measure of equipment performance before a change, an exact record of that change, and a re-evaluation of the effects of that change in the future. In practice, this is rarely the case.
Another problem is the complexity of building operations and human limitations in being able to account for all environmental/human variables occurring at once. For example, hot/cold complaints from tenants may lead building operators to adjust the set points of HVAC equipment. However, air temperature is only one of the factors that affect occupants’ perception of temperature. Humidity is at least as important, together with air movement, and the radiant heat balance. If the A/C is blasting, but internal humidity is high, people will feel like they are working in a refrigerator.
While the equipment needed to change humidity levels separate from cooling are expensive and almost never installed at the commercial level, it’s an important aspect to consider. If set-points are lowered or raised as a reaction, there may be higher costs without directly solving the problem.(source:enertiv)