Navigant Research Blog

The NFL Tackles Energy Efficiency

— October 12, 2014

On September 14, the San Francisco 49ers played the first game at their new home, Levi’s Stadium in Santa Clara, California.  Though it has its detractors, the new stadium is one of the most energy efficient sports venues in the world.  The 49ers partnered with clean energy leader NRG Energy to install a 375 kW solar power system across the stadium.  The installation will generate enough electricity annually to offset the power consumed during all home games.

In addition to onsite power generation, the stadium has installed low-flow water fixtures in all bathrooms, and water is reclaimed whenever possible to be reused for irrigation and other purposes.  A 27,000 SF green roof provides extra insulation and reduces the demand for heating and cooling.  Whenever possible, the builders used recycled and reclaimed materials during construction.  All of these features have led to Levi’s Stadium being the first U.S. professional football stadium to achieve LEED Gold certification.

Efficient Competition

Unfortunately for San Francisco fans, the 49ers lost their opening home game to another team that has made a commitment to sustainability.  The Chicago Bears completed a full renovation of the iconic Soldier Field in 2003, making it a goal to improve performance and efficiency while also reducing the stadium’s carbon footprint.  These efforts also earned recognition from the U.S. Green Building Council (USGBC) in the form of a LEED – Existing Building Certification.  Although Soldier Field does not have any onsite renewable power generation, it does boast many energy saving features, such as LED lighting with a networked control system and a green roof on the parking structure.

Given their very high energy usage, many other stadiums around the world have implemented efficiency features.  The most popular are efficient lighting/control systems and low-flow water fixtures.  More capital-intensive projects to install renewable power generation on stadiums are also becoming common.  Lincoln Financial Field, home of the Philadelphia Eagles, has the ability to generate 3,000 kW of renewable electricity onsite, the most of any stadium.  Eleven thousand solar panels have been installed, along with 14 eye-catching vertical axis wind turbines, which are intended to be a visual representation of the team’s commitment to sustainability.  FedEx Field outside of Washington, D.C. and MetLife Stadium in New Jersey boast 2,000 kW and 314 kW of generating capacity, respectively.

Power Houses

Two other highly efficient stadiums belong to two of the league’s top teams.  The Seattle Seahawks and the New England Patriots are both powerhouse teams, likely to meet in this season’s Super Bowl in Arizona.  Seattle’s CenturyLink Field produces 830,000 kWh annually with an onsite solar installation.  The Patriots’ home field in Foxborough, Massachusetts also features solar power generation, a 525 kW array installed by NRG Energy.  One of the distinctive features of this stadium is an integrated building energy management system that optimizes HVAC, lighting, and other systems.

Sports teams have a unique ability to influence their home communities in positive ways; their visible commitments to sustainability tend to have ripple effects throughout the community.  Energy efficient stadiums support local green businesses that are able to put their expertise on display in large-scale projects.  Saving energy and money and helping fans understand the impacts of their actions is a win for everyone.


Sunflower Concentrating Solar: 2,000 Suns You Can Touch

— October 6, 2014

A concentrating solar photovoltaic (PV) design from a Swiss company called D Solar shows a promising blend of multiple technologies that concentrates the sun by a factor of 2,000 but keeps the resulting temperature below the boiling point of water.

Concentrating solar uses mirrors to reflect sunlight onto a small PV chip to create electricity or on a heat collection liquid to create thermal energy.  The D Solar system does both at the same time.  The new design, called Sunflower, merges advanced concrete engineering with low-cost optics and a water cooling system designed by IBM scientists to provide a cheap method of turning sunlight into electricity and hot water.

At the heart of the Sunflower system is a receiver on which the sunlight is concentrated.  Any attempt at concentrating sunlight onto a PV cell faces a fundamental problem: concentrated sunlight gets too hot for the PV chip.  By running water through the chip at a high rate of speed, that heat can be carried away.  But cooling such a system is an extremely complex engineering task that requires space-age ceramics, precise flow control, and sturdy pumps.  IBM has been working on thermal control of computer chips at data centers, and its engineers saw a use for their cooling technology in the concentrating PV space.

Many Mirrors

Another fundamental problem of concentrating PV is that the mirrors or lenses used to concentrate the sunlight are often as expensive as the PV chips themselves.  To get around this, the Sunflower system uses stretched membranes of reflective plastic.  The Sunflower system resembles a large satellite dish, but instead of a sheer dish, the reflective area comprises multiple round mirrors, each consisting of a stretched foil that’s focused by putting it under vacuum pressure.  The pressure of the vacuum can alter the direction in which the foil reflects sunlight.  The entire dish is then covered by a bubble of another thin film of transparent plastic, which keeps dust, birds, and rain off the reflectors.

The sunlight is reflected onto a central receiver that contains the PV chip and the water-immersed ceramic receiver.  The dish is held up on a pylon of low-cost concrete, making all the materials in the device (save for the square inch of high-efficiency PV) very low cost.

Heat and Power

One of the economic attractions of the design is that, in addition to producing electricity from the PV chip, it also produces a significant amount of hot water, which can then be used for space heating, industrial processes, or even desalination.  The value of the electricity and the thermal energy together means more income can be produced by the same device.

While D Solar isn’t providing any cost estimates for the system (the small-scale prototype has not been completed yet), it’s clear that the design has the potential to be an extremely low-cost method of producing solar power.  While there have been many attempts at designing concentrating PV systems, none have quite been as unique and creative as the Sunflower system.


Wireless Power Could Transform Smart Building Nanogrids

— October 6, 2014

From mobile phones to Wi-Fi, wireless communications have fundamentally changed human behavior.  As the much hyped era of the Internet of Things looms, the dense, rich communication networks needed seem to only be possible using wireless networks.  Moreover, big data requires ever more data to be collected and shared.  In buildings, this means more sensors and more communications to enable better efficiency.  Though wireless communications are poised to facilitate this transformation, the shift remains tangled in the wired status quo.

In addition to communications, building networks need power to create what Navigant Research has defined as nanogrids, which are, in essence, single-building microgrids capable of aggregating and optimizing distributed energy resources (DER) while increasing resilience thanks to their ability to island during utility power grid outages.  Running power wires to sensors is costly in new construction and prohibitive in most existing buildings.  As a result, it’s not done unless absolutely necessary.  Wireless makes the communication side of the equation easily scalable.  The incremental cost for connecting more sensors is small.  But, if a sensor needs wired power, why would anyone invest in wireless communications?  Power remains the key to unlocking greater data density in smart buildings, and thereby, expanding near-term opportunities for nanogrid applications.

Get Low

One approach to reducing the cost of sensors is lowering the cost of power wiring rather than eliminating the wire all together.  This is accomplished by using low-voltage direct current (DC) power for sensors, controllers, actuators, and even LED lighting.  Low-power DC wiring doesn’t need to be installed by an electrician, reducing the installation cost.  Also, many electronic devices are natively DC-powered.  So alternating current (AC) power must first be converted, resulting in an efficiency loss.  Moreover, onsite generation of power through solar PV panels or wind turbines is typically DC (as are battery storage devices).  So, DC distribution within buildings helps match energy supply with loads (since according to some estimates, 80% of building loads such as LED lighting, laptops, and cellphone chargers are all natively DC).  Low-power DC in buildings can serve as building blocks to nanogrids that tailor energy services to the precise needs of end users.

The push for DC power is being led by the Emerge Alliance, an industry association developing DC power distribution standards for commercial buildings.  A competing solution can be found in Power over Ethernet.  Both solutions can be cheaper to install than a traditional system.  But, though low power is less intrusive than the status quo, wires remain a limiting factor.

Power from High Frequencies

Eliminating all wires is the most elegant solution to enable the transition to more data-rich buildings.  Currently, this is being done either by installing batteries or by harvesting ambient energy to power devices.  Batteries require replacement and, when examined on a cost per kilowatt-hour basis, are very expensive.  They just don’t provide enough benefit to eliminate power wires.  Energy harvesting, on the other hand, eliminates the maintenance requirement but is restricted by the ambient light available.

However, a shift from energy harvesting to wireless power transmission is on the horizon.  Ossia, a tech startup, has demoed its Cota wireless power technology and expects to have commercially available products by the end of 2015.  Cota works by broadcasting radio waves over the 2.4 to 2.485 GHz ISM band (the same as Wi-Fi, ZigBee, Bluetooth, and others) and is capable of transmitting about 1W of power up to 10 meters – enough for a sensor, but not much else.  Even a decade from now, it’s unlikely that wireless power transfer or energy harvesting will be able to provide enough power for anything more than a sensor.  But leveraging big data in buildings requires more sensors, many more than are currently deployed.  Wireless power could be the building block that brings the Internet of Things to smart buildings and hasten the spread of nanogrids.

For a more detailed look at the nanogrid market, please join our free webinar, The Expanding Business of Nanogrids, on Tuesday, October 14 at 2 p.m. ET.  Click here to register.


Power Sector Buzzes with Jargon

— October 2, 2014

As a utilities analyst, I encounter a number of buzzwords –  terms that seek to broadly and catchily define the multivariate technologies and approaches that have been developed to modernize the electric grid.  The most common are “smart grid,” “grid 2.0,” and “utility 2.0.”  In this post, I’d like to assist myself, and any interested reader, in better understanding these terms and how they differ.

Supposedly, the term smart grid was coined in 2003 by Andres Carvallo, then the CIO of Austin Energy, to explain the Electric Power Research Institute’s (EPRI’s) Intelligrid – an electric grid that was monitored and managed remotely and incorporated data analytics into processes.  The term didn’t really stick until 2009, when the U.S. Department of Energy (DOE) awarded 99 American utilities a total of $3.4 billion dollars as part of the American Recovery and Reinvestment Act of 2009 (ARRA)-funded Smart Grid Investment Grant.

So what does smart grid mean?  According to the DOE,  it means “computer based remote control and automation … made possible by 2-way communication technology and computer processing.”  Let’s just call it the foundational definition for all of the technological innovation that exists to modernize the electric grid.

One for the Shredder

As for the second, newer term, grid 2.0, it turns out that this buzzword didn’t really pick up that much, and as far as I could ascertain, it’s used synonymously with smart grid.  So we can just throw that one out right now and stop confusing people.

Utility 2.0, on the other hand, is an important conceptual extension from smart grid.  I’m pretty certain I first saw this word last year in reference to microgrids, in a Public Utilities Fortnightly article that explained how different technologies can enable grid resiliency and lessen the impacts of outages.  The term has also been used to describe the concept of utilities revising their decades-old business plans to take advantage of increased renewables generation, distributed energy penetration, advanced demand-side management, and customer engagement.  Last spring, the state of New York introduced its Utility 2.0 plan, which seeks to introduce regulatory incentives for utilities to fundamentally upgrade their business models, operations, and infrastructure.

Ignoring Complexity

The problem with the term utility 2.0 is that, in most cases, it’s used only in reference to how utilities do business, not to the technological and infrastructure considerations that enable this business.  In that sense, it indicates that utilities and regulators and customers are all going to work together, take some financial hits, and pay for and install a smart grid, and it’s all going to be great.  That simple definition ignores the most difficult parts of the process.

We’ve moved past the simple understanding of the smart grid.  We need to better understand the complexity of enabling different systems within the electric grid to function as a cohesive architecture.  This will be a different process for each utility because each system is uniquely configured to adapt to different constraints, and because there are so many different types of offerings out there that are targeted at similar issues.

So, to me, the term utility 2.0 is not just about reshaping business practices and integrating new technologies, such as distributed generation and demand response; it’s the systematic integration of diverse systems that allow for each utility to realize its own transformative goals.  This concept, also called interoperability, might be the single most enabling aspect of updating our electric infrastructure.


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