Storing Energy with Trains

ARES Image #4

Source: ARES North America

An earlier Future Friday post was titled Batteries: The Key to Renewable Energy Expansion.  A better title would have been Energy Storage: The Key to Renewable Energy Expansion.  Batteries are just one of many energy storage technologies currently in use.  One of the oldest and most well established technologies is pumped hydro-power.  Pumped hydro systems move water to a higher elevation during times of excess power, and release it to drive a turbine generator during times of increased demand.  Compressed air energy storage (CAES) systems operate on the same principle as pumped-hydro, using low-cost, excess power to store energy in the form of compressed air, which is released to drive a generator when power is needed. Other technologies include thermal storage (e.g., ice making for cooling) and flywheels that store energy as rotational inertia.  To learn more, the Energy Storage Association has detailed information on each of these technologies.

The trade-off with renewable energy sources such as solar and wind is that even though the fuel (i.e., sun and wind) is free the production is intermittent.  Intermittency is the primary roadblock to the expansion of renewable generation resources.  One way to address the intermittency problem is to store solar and wind energy in times of excess generation for times when production does not meet demand.

Advanced Rail Energy Storage (ARES) is currently testing a new, large-scale energy storage technology in Tehachapi, CA.  When power prices and demand are low the system drives electric rail cars carrying a load up an incline.  When demand and prices are high gravity pulls the trains back down hill turning the onboard electric motor into a generator.  When fully built out each train will haul a 230 ton load uphill, and be the equivalent of a 2 MW generator on the way down.  ARES’ website states that systems can be scaled as large as 3 GW, with 16-24 GWh of storage capacity.  Scalability is also a function of geography.  The system runs best on grades of 6 – 8%, and the longer the track, the more energy the system can store.  Currently, the system returns 86% of the energy used to drive the train uphill, though ARES believes this number can be improved.

ARES has already met with some commercial success.  They are working with Valley Electric, a Nevada-based electric co-op to build a 50 MW system with 12.5 MWh of storage capacity.  The goal is to have the system up and running by 2016.

Energy Star for Buildings Portfolio Manager Helps Improve Building Energy Efficiency

Energy-Star-logoThe U.S. Environmental Protection Agency’s (EPA) Energy Star is one of the most recognized brands in the U.S.  Eighty-seven percent of households recognize the Energy Star brand when they see the logo and 74% without seeing the logo.  Beyond recognition, 64% of households associate the brand with efficiency and energy savings.  Energy Star is a voluntary, market-based program to encourage energy efficiency and reduce emissions of greenhouse gases and other pollutants.  The label was first used in 1992 to identify energy efficient computers and monitors.  The Energy Star for Buildings program followed shortly thereafter, with the first pilot in 1993.  In 1999 EPA introduced Portfolio Manager, the centerpiece of the Energy Star for Buildings Program.

Energy Star Portfolio Managers is a free, online energy management and tracking tool.  Portfolio Manager helps companies track and measure whole building energy performance, including water use, greenhouse gas emissions, and cost.  Data is entered at the meter level, and Portfolio Manager has built-in accuracy checks and data wizards to assist with data entry.  There are almost 150 energy, water and greenhouse gas metrics available in Portfolio Manager, and users have the option of creating custom reports as well.  Portfolio Manager also has a planning function that lets users set baselines and targets for buildings.

One of the key features of Portfolio Manger is its benchmarking capabilities.  Not only are you able to compare the performance of buildings in your own portfolio, but to thousands of other buildings across the U.S. in the same sector.  Based on this comparison an Energy Star score from 1-100 will be assigned to a building.  For example, a score of 75 indicates that a building’s energy performance is better than 75% of the buildings in its sector.  Buildings that score 75 or higher, and have their data verified by a qualified third party, are eligible for EPA’s Energy Star for Buildings certification.  Portfolio Manager has 18 broad categories of buildings with 97 primary functions, of these only the 20 shown below are eligible for the Energy Star Certification.  The full list of building categories and primary functions can be found here.


By OscarUrdaneta (Own work) [CC-BY-SA-3.0 (], via Wikimedia Commons

●  Bank branch
●  Barracks
●  Financial office
●  K-12 school
●  Supermarket/grocery store
●  Wholesale club/supercenter
●  Hospital
●  Medical office
●  Senior care community
●  Hotel
●  Residential hall/dormitory
●  Office
●  Courthouse
●  Wastewater treatment plant
●  Worship facility
●  Retail store
●  Data center
●  Distribution center
●  Non-refrigerated warehouse
●  Refrigerated warehouse

Using Portfolio Manager to actively track and manage energy and water usage can yield significant benefits.  Energy Star Certified buildings average 35% lower energy usage and 35% lower greenhouse gas emissions than other buildings in their sector.  As outlined in a previous post: Building Efficiency Disclosure Expands in 2013, state and local jurisdictions are turning to Portfolio Manager to help drive efficiency improvements in commercial and multi-family residential buildings.  Given the broad recognition of the Energy Star brand, the Energy Star Certification also likely enhances reputational value as well.  EPA’s main Energy Star for Buildings website is here, and training on Portfolio Manager can be found here.

Building Efficiency Disclosure Expands in 2013

Three more cities joined the ranks of jurisdictions requiring buildings to disclose energy performance information.  Minneapolis, Boston, and Chicago all passed building energy performance disclosure ordinances in 2013.  Minneapolis and Boston’s ordinances are focused on non-residential buildings, while Chicago’s ordinance covers commercial, larger residential and government buildings.  This brings the total to 11 jurisdictions in the United States (2 states and 9 cities) requiring building energy performance disclosures.  In all, these disclosure policies cover 5.8 billion square feet of real estate in major markets in the U.S.



By Joshulove (Own work) [Public domain], via Wikimedia Commons

2013       Boston, MA
2013       Chicago, IL
2013       Minneapolis, MN
2012       Philadelphia, PA
2011       San Francisco, CA
2010       Seattle, WA
2009       New York, NY
2008       Austin, TX
2008       Washington, DC

2009       Washington state
2007       California


Why are more cities and states focusing on building energy performance?  According to the Department of Energy in 2010 the building sector accounted for 41% of annual energy use in the U.S.; more than either the industrial sector or the transportation sector.  In the global perspective, U.S. buildings accounted for 7% of worldwide energy use in 2010.  U.S. EPA data shows that when building energy use is consistently collected and benchmarked it leads to an average reduction in energy use of 2.4% per year, and a 7% reduction over three years.



Requiring building owners and managers to collect building energy information, and to benchmark against other buildings, provides the information needed to understand a building’s energy performance.   This also can help to identify opportunities to improve building energy efficiency.  Requiring disclosure creates a market-based incentive to improve building energy efficiency.  In those jurisdictions where disclosure is required the market will now judge buildings on energy performance as well as location, cost and other factors.

The existing building disclosure requirements share many similarities with regard to implementation.

  • All define disclosure requirements based on the square footage of the building, with disclosure requirements phased in for larger buildings first, expanded to smaller buildings over time
  • All of the programs cover commercial buildings
  • All use the U.S. Environmental Protection Agency’s Energy Star for Buildings Portfolio Manager as the system of record for building energy information, and to benchmark building energy performance

Despite these similarities some key differences exist as well:

  • In addition to commercial buildings some programs also cover multifamily residential (i.e. Austin, Boston, Chicago, DC, New York, and Seattle)
  • Required disclosure falls into two main categories with most programs requiring disclosure on a public website, while California, Washington State, Settle and Austin only require disclosure to transactional counter parties (e.g., sale, lease, finance)
  • Some programs require additional steps such as building energy audits (e.g. Austin and Boston)

The push to reap the economics and environmental benefits of more efficient building operation continues.  Both the state of Massachusetts and the city of Portland, Oregon are actively pursuing their own benchmarking and disclosure programs.  City level ordinances can be very impactful and should not be discounted.  Of the 11 existing ordinances New York City alone accounts for over 48% of square footage covered.  The top three jurisdictions are all cities and account for 70% of square footage.  More information on the existing ordinances can be found at the website, which includes this helpful Commercial Building Policy matrix.  In a future blog post I’ll cover the main tool used by all the building efficiency disclosure policies, EPA’s Energy Start for Buildings Portfolio Manager.