Your questions answered: How to future-proof HVAC systems to meet efficiency and carbon emission goals

Presenters from the July 15, 2020, webcast “How to future-proof HVAC systems to meet efficiency and carbon emission goals” replied to questions not addressed during the live event. Presenters included:

• Drew Turner, Global Marketing Manager, Danfoss Oil-Free Solutions
• John Sheff, Director of Public & Industry Affairs, Danfoss
• Ken Koehler, Senior Business Development Manager, Danfoss

Question: How we can reduce gas emission for carbon production and what is the impact on HVAC?

Danfoss: Not certain I understand the question, but believe it has to do with the impact of building HVAC systems on carbon emissions and therefore ability to reduce them. Buildings are responsible for ~39% of carbon emissions and HVAC/lighting is responsible for ~28%. The solutions discussed in the webcast, such as variable speed compression, present significant carbon reduction potential.

Question: Do you think the localized cogeneration applications at sites will be reduced due to lack of gas facilities and decarbonization?

Danfoss: On-site fossil fuel-sourced power generation will be impacted by the move to renewables, but relative to the efficiency and resulting carbon reduction potential. Cogeneration that makes use of the heat as well as the power produced has lower potential carbon emissions reduction than those that don’t. If the on-site generation is also participating in grid services demand response programs, there is less drive to replace it.

Question: So, if we have 54% carbon free power, what reduction in carbon is that from natural has? What does 1% get you leveraged in pounds?

Danfoss: It depends on the fossil fuel power source that you’re replacing. The Energy Information Agency has good detail on the CO₂ emissions associated with specific sources. If you replace 46% of combined cycle natural gas with renewables then you’ll get an approximately equivalent reduction in CO₂ emissions. Or per the link, reduce 117 pounds of CO₂ for every MMBtu replaced.

Question: Which government or private buildings have connected or coupled their thermal and cooling systems?

Danfoss: In the public and private sector, this coupling or combining of heating and cooling systems is just beginning. Certainly, we will see this trend continue in new construction as electrification technology improves and policies mount to encourage this practice. In retrofit projects, more policies like the ones we discussed in New York City and Washington, D.C., are needed to spur this coupling because this retrofit project can be expensive.

Question: In residential buildings, inverter-driven modern heat pumps routinely use variable speed technology and are widely used. Correct?

Danfoss: These systems are more widely used outside of North America and they are known as “mini splits” and the efficiency is two to three times higher for converter-driven air conditioners and heat pumps. However, the cost of standard split system air conditioners and heat pumps with inverter-controlled compressors cost 25% to 55% more than single-stage and two-stage systems of the same size.

Question: In residential applications, it is often referred to as electrotonically commutated motors, which are variable speed.

Danfoss: Yes, this is true for residential fan motors. In residential air conditioning units, the tonnage is smaller, allowing for or electrotonically commutated motors to be used for variable speed control of the fan. Generally, variable speed compressors in residential units are relatively rare. In larger commercial applications, ECMs are not applicable so variable frequency drives are typically applied.

Question: Do you have samples of life cycle cost analysis of variable speed compressor chiller versus “traditional” chillers?

Danfoss: Danfoss has a “Chiller ROI” app available for free from the App Store where you can compare two chillers.

Question: What is the preferred heat/cool energy storage you mentioned in the water-based district energy systems?

Danfoss: The great thing about a district energy system mentioned in the presentation is that it has some level of built-in thermal storage based on the flywheel effect of the loop itself. The other great thing is that it provides multiple options for additional storage type and location. More common district energy thermal storage systems are heating or cooling storage tanks, generally located near the central heating/cooling source generation. Ground storage is becoming more common.

Question: Any comments on recent announcements from the Department of Energy’s Office of Energy Efficiency & Renewable Energy from July 14, 2020: DOE Releases Draft Energy Storage Grand Challenge Roadmap and Requests Stakeholder Input?

Danfoss: It’s great to see the DOE’s Office of Energy Efficiency and Renewable Energy putting so much energy and funds toward the goal of increasing efficiency and renewable energy in the built environment.

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