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How Dual Energy Can Make a Difference in Commercial, Institutional and Multi-unit Rental Buildings

January 24, 2024    4 min.

Since November 6, Énergir, in conjunction with Hydro-Québec and Écoperformance, has been offering its commercial and institutional dual-energy program to its commercial, institutional and multi-unit residential clients. This program, which is in addition to existing energy efficiency programs, will accelerate decarbonization of buildings by leveraging the complementarity between hydro power and natural gas. How can dual energy reduce building energy bills and greenhouse gas (GHG) emissions? And what role can renewable natural gas (RNG) play in the equation? We’ll tell you about that and more in this article.

How does dual energy work?

Dual energy involves electrifying a building’s heating system while maintaining natural gas heating. So long as the outside temperature remains above -12°C (or -15°C for customers in Abitibi and the Saguenay), the electrical system provides the heat. When the temperature falls below the threshold, the gas-powered equipment takes over to take pressure off the power grid. Depending on the type and capacity of the electrical equipment used, natural gas (and therefore GHG) savings can be as high as 70% to 80%.

Fictitious decarbonization scenario in a school

To help you understand how this solution works in practice and compare the benefits under the different scenarios, let’s look at a fictitious example of decarbonizing a school.

Initial situation:

High school with a 2000 MBH boiler used to heat the building via a hydronic system. The boiler uses 90,000 m3 of natural gas annually. The boiler aside, we’re assuming that the school has already optimized its energy performance (all cost-effective measures have been subsidized by our programs).

  • A - All-gas scenario: Replace the existing boiler with a high efficiency boiler.
  • B - Standard all-electric scenario: Replace the gas-powered heat source with a 400 kW electric boiler.
  • C - Efficient all-electric scenario: Replace the gas-powered heat source with heat pump units.
  • D - Efficient dual-energy scenario: Install air-water heat pumps on the hot water loop. Under a conservative scenario, we consider that heat pumps can heat the building in temperatures as low as -12°C. To achieve this, twelve 15-ton heat pumps are required.
  • E – Efficient RNG dual-scenario: This scenario is the same as scenario D, but uses renewable natural gas (RNG) instead of conventional natural gas.
- Baseline consumption for heating: 90,000 m3
- Gas efficiency: 80%
- Molecule price: 15¢/m3
- CATS Price: 9,128¢/m3
- Remaining gas components: Effective August 2023

Simulation results:*

100% gas Standard all-electric Efficient all-electric Efficient dual energy Efficient dual energy + RNG
CAPEX $76,320.00 $50,000.00 $446,000.00 $472,320.00 $472,320.00
OPEX Total $46,265.45 $101,263.20 $85,983.47 $34,634.90 $42,997.49
m3 90,000 0 0 18,102 18,102
GHG (t/year) 191 0 0 34.8 0
kW max heating 0 395 395 190.5 190.5
kWh 0 757,440 505,315 365,903 365,903

Dual energy makes a difference

As the results above show, significant reductions in GHG emissions are achieved with all of the scenarios. Since we’re fortunate to have clean electricity in Quebec, complete electrification eliminates virtually all the building’s emissions. But full electrification of the building requires more than double the electrical power of the efficient dual-energy scenario.

How can we reduce GHGs to the same level as with full electrification without monopolizing too much power during peak winter periods? That’s where renewable natural gas (RNG) comes in. By combining the new dual-energy program with RNG, we achieve a carbon footprint similar to Scenario B (100% electric) without using all the electricity, availability of which may be limited depending on the region. What’s more, there are major differences in annual energy costs between Option B and Option C and Option E. In today’s energy environment, power savings could help finance more projects, ultimately reducing GHG emissions even more.

In order to meet demand from small and large consumers who want to use dual energy to decarbonize their building heating systems, the Government of Quebec, Hydro-Québec and Énergir have created two grant application streams (simplified and custom). The amounts available under the two options are described below:

Stream Simplified Custom
Grant 80% of the additional cost Minimum between 80% of the additional cost or $250/tonne of GHG for 10 years.
Maximum per project $150,000 $3,000,000
Maximum per address $250,000 $6,000,000

In our example, the grant for switching to dual energy would be $390,500 under the custom option.

Cooling and ventilating our schools with dual energy

The case presented above is relatively straightforward, but for aging and heterogeneous building stock, it’s obvious that we'll need to look at other approaches to dual-energy conversion can be analysed. For example, funding could be requested to upgrade a school’s ventilation and air conditioning system – a scenario that could be applied on a broad scale given the significant ventilation and air conditioning needs of Quebec schools.

Starting from the same initial situation, it would be possible to add mechanical ventilation at the school by installing new air units. Preheating and conditioning of outdoor air could be ensured through heat recovery and aerothermal heat pumps. To minimize ductwork space requirements, a variable refrigerant system called a “VRF" could be considered. Fan coils installed in classrooms could heat and cool the thermal envelope via the new heat pumps. The building’s existing hot water loop would be more useful than ever, as it would be possible to switch to natural gas to provide heat when temperatures fall below -12°C (or -15°C for Abitibi and Saguenay) or to keep occupants comfortable. In addition, heat pump sizing could be based solely on the air conditioning load. However, low temperature limits for heating with the units would still need to be calculated in order to accurately assess the GHG savings.

This configuration would not only provide heating and cooling according to the season, in addition to providing classrooms with mechanical ventilation. Given that adding air conditioning would allow the deployment of dual energy, the additional installation costs would be subsidized at a rate of $250/tonne of GHGs or up to 80% of the investment, a major incentive to boost students and teachers’ well-being, improve indoor air quality, and reduce the building’s carbon footprint.

Configuration example

Current situation - not air-conditioned
Proposed dual-energy situation - addition of air conditioning/heating

Think decarbonization

Although fictitious, the examples presented in this article clearly show the potential of dual energy for decarbonization. This strategy, backed by a proper needs analysis and feasibility study, will enable managers and owners of commercial and institutional buildings to move forward to reduce GHGs while at the same time enjoying associated benefits in terms of energy consumption, sustainability, and social responsibility.

The Datech team can help you assess your options of decarbonization!

Learn more about commercial and institutional dual energy,
Go to the Engineers section for all our documentation

Martin Brière-Provencher.
Senior Advisor, Energy expertise
DATECH Group – Development and technical assistance

* The capital expenditures in the simulation do not take into account the cost of upgrading electrical inputs and installation. Only equipment costs are considered.

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