Recap: A Presentation on Passive Thermal Energy Storage… for Business Folks

There is a lot going on in the world of energy management and energy efficiency. Unless your full-time job is in energy management, it’s tough to keep up with this field. Just recently, CoEng Advisors gave a presentation on a new technological approach we use in making buildings more energy efficient, so we’d like to share a recap on it — not just for engineers, but also for business decision-makers, who manage their organizations’ operations, finances, sustainability, and corporate social responsibility, or run a small or medium-sized business of their own.

This blog post covers a talk from Wednesday February 8 presented by our Founder and Director of Engineering, John Molnar, at the first chapter meeting of 2017 for the Association of Energy Engineers Southern Ontario Chapter.


So, what can someone on the business side take away from this presentation for engineers? For starters, they can learn about…

  • Energy management approaches and technologies for their business’s operations, and
  • Seeing the “bigger picture”: economy, society, and the environment in Ontario and around the world.

All in all, this talk was not only about how energy managers do what they do, but also about why they do it. Let’s go!


(Source: AEESOC website)

Energy Efficiency Options: Looking at Passive Thermal Energy Storage

In Ontario, as in many other jurisdictions, the price charged for the electricity in buildings varies depending on its Time of Use (ToU). The Passive Thermal Energy Storage (TES) approach is one way to shift a building’s draw of electricity from the most expensive peak times of use to the least expensive off-peak times, essentially taking in energy at its lowest ToU price to stock up for use throughout the day.

With this energy storage being thermal, it shifts the ToU of the electricity that powers the HVAC (Heating, Ventilation, and Air Conditioning) systems of the building. CoEng Advisors for example, use this approach specifically for building cooling in the summer. Then, with this energy storage type being passive, it takes the materials within the building itself into account as the means of storing the thermal energy. As John clarified (with a laugh), “We’re not actually putting batteries in your walls” with this approach… but it does use the walls, floors, ceilings, and furnishings in the building like batteries.


The Passive Thermal Energy Storage concept: ““We’re not actually putting batteries in your walls” with this approach… but it does use the walls, floors, ceilings, and furnishings in the building like batteries.”

Another type of energy storage for buildings that you might be familiar with is Active TES, which actively makes additional heating and/or cooling efforts to be saved for later. A third energy storage type is Electrical, which sets energy aside as an input for generating electricity or to be directly discharged as stored electricity later. Both these types differ from Passive TES in that they require investments into added equipment and need active inputs of energy into those systems to be stored for later use. Meanwhile, Passive TES works with the systems and materials that already exist in the building!

Data & Analytics: The Keys to Doing Passive TES Right!

John explained that the Passive TES approach is best implemented using a Model Predictive Control system (CoEng Advisors use a cloud-based MPC system). The MPC links data on the building operations with those on grid operations to run a detailed analysis. In a bit more detail…

  • The MPC models the building and combines in the following data: electricity prices for different ToU, outdoor temperatures, and real-time data on the building’s temperature and the electricity grid’s Demand Response (DR) requirement and/or Load Dispatch strategy. With this data…
  • It determines the most energy-efficient, most cost-effective, and lowest emissions strategy for operating the building’s cooling system. Then from there…
  • It connects with the existing Building Automation System (BAS) to simply periodically change room temperatures and communicate with the grid operator.


Visualizing the Model Predictive Control system and its communications

Load Shifting and 4 Other Reasons Engineers Opt for Passive TES

Energy efficiency brings cost savings because while the amount of energy consumed is reduced, obviously so is the cost for using it. Managers can also cut down on costs simply by shifting their building’s electricity load from more expensive to less expensive ToU periods in the day. That load shifting is the #1 way that Passive TES decreases energy costs in building operations, and… it isn’t the only way it brings big savings. Here are the others:

  1. Reducing Peak kW: In Ontario, Class A electricity customers can save $500,000/year for each MW of demand they reduce at peak time. (And we’ve seen an average reduction of 30% for peak cooling electrical demand where this Passive TES approach has been applied!)
  2. Allowing Focus Within the Chiller Curve for Load Shifting: There are certain points in the chiller curve where it runs most efficiently. Passive (as well as Active) TES allows us to shift the load to the most efficient operating point of the chiller itself — again, lowering kWh.
  3. Improved Mechanical Efficiency for Cooling: Like any mechanical system, HVAC systems will produce the best results when they work under the best operating conditions and/or to less strenuous performance levels. One specific reason factoring into the improved cooling efficiency from Passive TES is that the chiller Entering Water Temperature (EWT) is already cooler at night, so the chillers do not need to work so hard to produce chilled water for air conditioning. Another gain is that the pumps and fans will only need to run at part-load performance, which saves even more kWh and peak kW.
  4. Frees Up Human Hours for Other Tasks: The MPC system automates a multitude of operations activities! This frees up a great deal of time for operations staff to be able to work on other important tasks at hand. In the case of one client, they are saving 100 human days of labour by further automation that the existing BAS was not equipped to execute. Now the building operators can focus on maintaining the cooling system in good and reliable operation.

The Big Picture Reasons

Before giving a walk-through of Passive TES, John discussed the concerns for reducing energy consumption in the first place. We’ve already covered how it decreases operating costs for businesses, like any other energy efficiency measure would (and we all know that healthier businesses contribute to healthier economies), but there are some excellent reasons in the broader scope, such as:

  1. The Central Environmental Reason — Climate Change: As long as we use fossil fuels to generate power (28% of connected power generation in Ontario is gas), our electricity demand will be linked to greenhouse gas (GHG) emissions. These emissions contribute to climate change, affecting not only our environment, but also society and the economy. However, we can make an impact by reducing our overall demand for electricity and the share of it we generate from fossil fuels.
  2. If You Thought Natural Gas Was a Lesser Evil, Think Again: Of course, GHGs are emitted from power generation when natural gas is used there, but thus far that’s been a sacrifice we have been willing to make. Recently, we have also learned of underestimating in gas losses and GHG emissions tied to natural gas production and transmission, which preclude its use in generating electricity. Another point to consider is that natural gas has a cost for each unit consumed as an energy input and since it is not renewable.
  3. Peak Generation Is Provided by Gas Power: There is no doubt that Ontario has a rather diverse energy mix in its electricity generation compared to other areas. As already mentioned, however, fossil fuels still make up the second largest share of electricity (after nuclear) and to top it off, gas power is used to ramp up electricity generation for our peak periods. If we can reduce that need for such a high peak, then we can reduce our dependency on natural gas.

Coming back to Passive TES: It is an approach that helps mitigate these issues related to our buildings’ energy use and related to our whole electricity grid in Ontario.

The Full Presentation

Again, this has been just a recap of our Founder and Director of Engineering, John Molnar’s presentation last month at AEESOC. If this blog post has you intrigued to learn more in greater detail, check out our Facebook page, where the full presentation is available on video along with slides at the following link:

presentation video screenshot.png


One thought on “Recap: A Presentation on Passive Thermal Energy Storage… for Business Folks

  1. Pingback: The Energy Waste Sensei — Peak Shifting Strategy, Part 2 | Energized

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