Navigant Research Blog

Refrigeration’s Chilling Effect on Energy Efficiency

— August 6, 2014

China’s meteoric rise has had profound impacts on its economy, people, and environment.  Navigant Research has examined the consequences this growth has on energy used by buildings and cities.   As the country of 1.3 billion becomes more prosperous, the next transformation occurring is in cold storage.  In a recent article, The New York Times Magazine delved into the adoption of refrigeration in China.  On the consumer level, China’s domestic refrigerator ownership has grown from just 7 % in 1995 to 95% in 2007.  As a result, the cold chain (the temperature-controlled storage and distribution infrastructure) is growing as well.

The United States, which leads the world in cold storage, currently has about 3 times the cold storage per capita as China does.  In China, less than one-quarter of meat and 5% of fruits and vegetables travel through a cold chain, compared to about 70% of U.S. food.  As China’s living standards rise, refrigeration and energy use are set to explode.  Currently, cooling accounts for only about 15% of global electricity consumption.

The threat associated with increased living standards is not isolated to China.  An estimated 40% of fruits and vegetables in India are lost to spoilage as a result of poor infrastructure.  Although the Indian economy has not performed as robustly as China’s, there is hope that growth will pick up shortly.  However, with that hope comes the risk of unsustainable energy consumption on a staggering scale, as India and China combined account for more than one-third of the world’s population.  As such, vast advances in the energy efficiency of refrigeration are needed.

Birth of the Cool

Refrigeration, like air conditioning, relies on the vapor compression cycle.  The vapor of a refrigerant is compressed to the point where it is superheated and then travels through a condenser where heat is rejected from the refrigerant vapor and it is condensed into a liquid.  Next, the liquid goes through a throttle valve where it evaporates into a low-temperature, low-pressure mixture of liquid and vapor.  Lastly, this mixture travels through an evaporator that absorbs heat from the space being refrigerated and evaporates the mixture so that it can be compressed and the cycle can start again.

Incremental improvements have been made in the efficiency of refrigeration, but there is a physical limit to how efficient the vapor compression refrigeration cycle can be.  It may be time to rethink the fundamentals of refrigeration.  The U.S. Department of Energy, for instance, has been investigating the use of non-vapor compression technology.  But the answer may not be cooling at all.  Cooling is a means to an end; it is an effective method of inhibiting microbial growth.  But it is not the only method to do so.  Fenugreen FreshPaper uses naturally occurring antimicrobials to keep fruits and vegetables fresher longer – with near-zero energy use.

 

Energy Efficient Solutions for Retail Stores Begin to Emerge

— July 23, 2014

The retail landscape is in flux, to say the least.  Earlier this year, Staples announced the closure of 225 stores.  Troubled Best Buy isn’t closing any stores this year, but it was one of several retailers to close stores in 2013.  Things aren’t all so bleak for big box retail, though.  Costco is in the midst of a 5-year plan to open 150 new stores.  Meanwhile, Walmart announced a strategy of shifting toward 10,000 SF to 40,000 SF grocery and convenience-type stores, away from 200,000 SF superstores.  Large retailers are rethinking their physical footprint.  Part of the shifting landscape comes down to the fact that brick-and-mortar stores, particularly warehouse-type stores, are costly to operate.  Moreover, the energy efficient operation of these assets is hindered by factors such as unpredictable occupancy, high ceilings, and vast open space.  Yet, smart building technologies are being developed for the specific challenges that face retail buildings.

There are numerous approaches to improving the energy efficiency of buildings (see Navigant Research’s reports Energy Efficiency Retrofits for Commercial and Public Buildings and Building Energy Management Systems).  But many of these aren’t appropriate for large, big box retail buildings.  A recent brief from Johnson Controls’ Institute for Building Efficiency provides a thorough analysis that quantifies the cost and payback of various building efficiency improvements for commercial office buildings.  It details 16 measures that represent 90% of possible energy savings.  Unfortunately, most of those do not address big box retail; they focus on using energy for building occupants, not for empty spaces.  That translates to providing cooling, lighting, and even power for computers only when occupants are in the space.  Although these measures work in office buildings, healthcare facilities, schools, and many other commercial buildings, they don’t provide the same opportunity to many retail spaces.

What Does Smart Retail Look Like?

Many retailers have aggressively pursued demand-controlled ventilation, lighting and controls upgrades, and advanced efficiency compressors for HVAC and refrigeration to reduce operating costs.  But the cutting edge of smart building technology for retailers focuses more on the consumer experience than on energy efficiency.  GE Lighting and BryteLight, for instance, are using next-generation LED fixtures to provide location-based services for retailers.  Similarly, the Open Group, a consortium that enables the achievement of business objectives through IT standards, has outlined a use case of using sensors to provide real-time information to retail customers.

However, MIT’s SENSEable City Lab has recently unveiled a concept to use smart sensing technology to reduce energy consumption.  Local Warming creates a controllable heating zone around an individual occupant, leaving the rest of the space at a neutral temperature.  The solution relies upon a Wi-Fi-based motion tracking system that controls a system of mirrors and rotating motors to direct an infrared energy beam onto an occupant.  In the future, LED technology can further reduce the complexity of the system by allowing a more distributed source of infrared heat.

Local Warming Concept

(Source: SENSEable City Lab)

While the system is not specifically designed for retail, the most compelling application for Local Warming is clearly big box retail.  These retail spaces are typically large and sparsely occupied.  Additionally, infrared heating has long been employed in large retail spaces.  Infrared heaters, which transfer heat through radiation rather than convection, warm occupants without having to warm the air.  In warehouse-like stores, with lots of air relative to the number of people in it, infrared provides an efficient method of heating.  Local Warming may signal a shift in the use of advanced sensor and location-based services in retail to the development of more advanced efficiency solutions.

 

Li-Fi Turns Light into a Data Stream

— July 13, 2014

Since Harald Haas demonstrated the ability of light-emitting diode (LED) lights to transmit data during a TED Talk in 2011, the promise of Li-Fi (short for light fidelity) has received a lot of attention.  As researchers develop faster and faster communication speeds, the application of the technology to the building space appears both realistic and attractive.  Commercially, General Electric (GE) has demonstrated the viability of the technology through its launch of LED-based communication for retail environments.  Li-Fi could be cheaper and consume less energy than existing wireless communication technologies that rely on radio frequencies (RF).  Smart buildings, which require a dense and flexible control network, present an interesting application for a Li-Fi deployment, particularly with the increased adoption of LED lighting.

Non-Interfering

Li-Fi seems to be a compelling alternative to the RF technologies that are currently in use today.  First, the RF available to building automation is crowded.  Moreover, as the Internet of Things becomes more pervasive, more and more communication nodes will further saturate the environment.  RF travels through walls.  So, a node in an adjacent room will be competing for detection.  But Li-Fi is impervious to this problem.  Since the range of any individual Li-Fi node extends only to the nearest wall, the communication in one room will never interfere with other communication in a different room.  In other words, the inherent limitations on Li-Fi range are an ideal solution for saturated networks.  Moreover, more than just crowding, interference from microwaves and other devices can be a problem, particularly in medical environments.  Li-Fi is immune to RF interference.

Security is another area of concern for wireless communication.  It’s relatively easy to hack a Wi-Fi network.  Li-Fi, on the other hand, has a shorter range and requires line-of-sight.  As a result, it is inherently more secure.  You have to be within the range of the transmitter and receiver, shifting the threat of IT security to more manageable physical security.

The Bad News

The technology faces some serious technical challenges before widespread adoption, though.  In addition to enhancing security, the line-of-sight requirement also presents challenges.  Though Li-Fi is immune to RF interference, it is susceptible to interference from a more ubiquitous source: the sun.  Receivers placed close to windows could be rendered ineffective.  Additionally, lighting in buildings is typically designed to be unidirectional, from the light source to the space to be illuminated.  But communication networks must be bidirectional to both send and receive data.   In order to create a Li-Fi network, lights would need to be installed to point at each other, which is at odds with their intended functionality.

Despite these drawbacks, Li-Fi could overcome several of the barriers facing wireless.  Though most of the current buzz focuses on visible light communication, using infrared light could solve many of the hurdles.  Windows can be designed to block infrared light but allow visible light to pass, eliminating problems of solar interference.  Infrared also has greater potential throughput of up to 5 to 10 gigabits per second.  Overall, the challenges facing Li-Fi are no greater that the challenges facing RF.  The technology appears to be several years away from successful deployment in building automation.  But it’s coming.

 

Green Buildings Get Capital Vote

— July 2, 2014

While Congress drags its heels on climate change legislation, the District of Columbia has become a leader in green building requirements.  The D.C. Green Building Act of 2006 requires that all new private development projects 50,000 SF or larger qualify for the LEED-certified designation.  As a result, Washington not only has more LEED-certified buildings than many states, but also has the second-largest number of ENERGY STAR-certified buildings of any city in the United States (Los Angeles is first).  As the number of green buildings in the nation’s capital increases, attention is being focused on the actual energy efficiency performance of these buildings.

The Washington Examiner, a local tabloid, provided a shockingly poor analysis of the impact that LEED certification has on buildings in D.C.  The report looks at data provided by the district government on energy intensity based on actual utility bills to determine if buildings constructed to LEED standards are more efficient than buildings that are not.   The analysis examines the performance of buildings over a set period of time and compares a group of LEED buildings to non-LEED buildings.  But buildings are considered to be LEED buildings if construction to meet LEED standards has been completed, is ongoing, or is even just planned as future work.  Examining projects such as Ballou High School (estimated completion date: June 2015), Stuart-Hobson Middle School (December 2015), and Lafayette Elementary School (August 2016), the report overlooks the fact that the performance benefits of building to LEED standards are not realized until after construction.  Rather than conclude that the buildings with the poor energy performance were chosen to be renovated to meet LEED standards, it concludes, bizarrely, that LEED standards are meaningless.

Commissioning Key

Though it may be easy to dismiss this analysis outright, it raises an important question about how to ensure that a building’s performance is aligned with its design.  During operation, buildings drift toward inefficiency.  Periodic commissioning of mechanical, electrical, and plumbing systems can optimize the building’s performance.  (This process is described in Navigant Research’s report, Building Optimization and Commissioning Services, from 2012).  Indeed, the LEED standard for new construction requires fundamental commissioning of buildings and provides an additional credit for enhanced commissioning.  However, commissioning is rarely repeated more than once every 3 to 5 years.  The drift in building performance is an opportunity for new approaches to energy savings.

The U.S. Green Building Council (USGBC) is attempting to capitalize on this opportunity through the launch of its dynamic plaque, which provides an ongoing LEED rating to measure and display a building’s rating in close to real time.  But a dynamic plaque still needs an operator to diagnose and address changes in performance.  The future of well-tuned buildings lies in ongoing commissioning, which automates the process.  Solutions available from several building energy management system vendors not only monitor performance, but also detect anomalies and recalibrate the control system to meet ideal parameters.  By applying fault detection and diagnostics-based algorithms that track individual control and equipment performance on an ongoing basis, continuous commissioning provides the best opportunity to guarantee that green buildings are energy efficient buildings.

 

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