A report by the American Council for an Energy-Efficient Economy (ACEEE) has found that retrofitting smart technology to commercial buildings can cut energy bills by 18% in offices, 14% in shops and 8% in hospitals.
The report considers the cost and benefit of a wide range of options that are open to building owners and managers now, including, among others, occupancy sensors, smart thermostats, demand-controlled ventilation, electronic films for windows, automatic shading systems, tenant comfort feedback systems, smart plugs and cloud-based energy management information systems.
Although many building owners in the US are aware these options exist, many are unsure how to make them work, what the savings might be and what the cybersecurity risks are. The report sets out to show how buildings in four commercial sub-markets can benefit by upgrading their systems.
Smartening second class offices
Recently built “class A” offices generally come with sophisticated interoperable systems already in place. However, most of America’s one million office buildings do not fall into that category and have to be retrofitted, which raises the problem of where to make investments and how to understand the accompanying risks and benefits.
The report points out that there are some low-hanging fruit for an owner looking to retrofit a class B office. The lowest of all is to upgrade the lighting system. This can be done by hiring a light service provider to fit efficient lamps and controls at no up-front cost. Energy savings from the upgrade are used to pay off the provider over the terms of the agreement.
Another relatively painless choice is to fit wireless thermostats that turn off the heating if nobody is present. This can save up to 10% of total heating, ventilation and air-conditioning (HVAC) costs. The report is cooler on the benefits of a learning thermostat, on the grounds that preliminary trials of the Nest product in commercial buildings suggested it was difficult to prove they saved more energy than a regular smart thermostat.
The report also recommends the fitting of sub-meters, so that the tenant can be charged for the electricity they actually use. For an outlay of $2,000-4,000 a network can be set up in a typical office.
The report notes that more than half of all American offices use rooftop HVAC packages. If these are fitted with smart control, wireless carbon dioxide sensors and variable speed drives (VSDs) – to allow variable fan speeds – then HVAC costs can be cut by between 20% and 40%.
Another quick win is to fit smart solar films to windows. These can be programmed to adjust the amount of incoming sunlight, and can thereby reduce cooling load by 10-20%. This option has the advantage of being easy to retrofit, and also allows users to control their environment by dimming windows using their smartphones.
Retail, hospitality and healthcare
All the options that can be deployed in a class B office also apply to a retail unit, although the costs and the returns are somewhat different owing to the differing use patterns of the two building types. In particular, lighting is a more important consideration in a retail sales area than in an office.
As an example of how shops can raise their game, the report includes a case study of Macy’s department story in Washington, DC. This is fitted with two air-handling units, with 400HP of supply and return fans.
Although the fan motors were already equipped with VSDs, and the units ran as they were designed, the store found that by upgrading the dampers and controls, switching to low energy lighting and reprogramming its building automation system to distribute air more efficiently, it could cut energy consumption by 30%.
Another case study illustrated how hotel owners can benefit from cloud computing to understand their building. The Hilton chain worked with an analytics company called Entic to install sensors and software in some test sites. These used wireless cloud storage to record a hotel’s 4,000 data points, which allowed building services engineers to see where problems were occurring and to prioritise remedial action.
This concept, which Hilton calls “constant commissioning”, has opened up the prospect of savings across the business of $1.2m per year. As with smart lighting, Entic collects its fees from savings, making this kind of retrofit easy to finance.
For healthcare, the report considers the medium-sized non-teaching facilities that make up the bulk of America’s 9,579 hospitals.
The report points out that 69% of these buildings already have automation systems in place, which acts as a framework for new smart systems. For example, a combination of the internet of things and energy-management information system will “coordinate with the surgical schedule to ensure that room conditions are appropriate for a given procedure and to save energy when the room is vacant”.
Furthermore, because hospitals are already high-tech environments where mobile technologies and data analytics are part of everyday life “it is reasonable to assume that they are primed to adopt other technologies to manage energy consumption”. And because a hospital uses three times as much energy per square foot than an office, and has a longer and more predictable operational life, building managers can count on long payback periods for investment.
The report, Smart Buildings: A Deeper Dive into Market Segments, by Christopher Perry, can be downloaded here.
Top image: Manhattan, New York: Most of America’s one million office buildings could be retrofitted (Wikimedia Commons)
