Bernhard's Decarbonization Solutions for Cold-Climate Clients

Culture of Innovation

Innovation is at the core of what we do. In order to truly innovate, our engineers, researchers, and analysts are encouraged to break new ground and push the boundaries of science and engineering to find innovative, outside-the-box decarbonization solutions that will benefit our clients and economy for years to come.

By instilling this culture of out-of-the-box thinking without fear of “being wrong” our experts are free to explore any energy solution until they eventually find the perfect outcome for our clients. Where other firms may criticize an idea that doesn’t work, we applaud it because that means we are one step closer to finding a solution. This culture of unapologetic innovation is how Bernhard remains on the cutting edge of the Energy-as-a-Service industry.

The Heat is On

A major challenge faces Bernhard’s customers as they strive to phase out carbon-heavy gas systems in favor of more sustainable electricity. In cold climates, current technology forces them to use electric resistance heat which causes their energy use to skyrocket. To avoid this, our team has been seeking a practical alternative to electric resistance heat.

In a perfect world, a large hospital or university in Minnesota or Michigan could store heat from its rooftops all summer long, then utilize it to warm interior spaces the following winter. If possible, such an approach would substantially reduce the energy required to heat facilities in winter months.

Bernhard was asked to investigate just such a solution for a client in the Northwestern United States. This client is located in a city that experiences long, cold winters, with average January highs in the mid-20s and lows near or below zero. But notwithstanding the cold climate, this client has committed to net-zero carbon emissions within the next few years.

HEAT PUMPS 101

Facility owners wishing to eliminate natural gas heating are forced to consider electric heating options. You can heat a structure with electricity in the winter in one of two ways: generate heat with electric resistance (think of the glowing orange heating element inside a toaster) or you can scavenge heat from the environment and transfer it indoors using a refrigeration cycle.

Heat pumps are all-electric and use a refrigeration cycle. It’s complicated, but to summarize the process, a refrigerant cycle transfers heat from one location to another.

For example, a home air conditioning unit may pull air from a 75-degree room, cool it down, and blow 55-degree air back into the room. It has removed heat from the air, but where did the heat go? Refrigerant from the cooling coil absorbed heat and sent it through copper lines to the outdoor unit. There, a compressor squeezed the refrigerant to make it hot, and a fan blew across the hot refrigerant to cool it off. The system didn’t create hot air or cool air. It removed heat from one location and moved it to another. An air-conditioning system removes heat from indoor spaces and sends it outdoors.

A heat pump works the same way as an air conditioning system, the difference being that instead of cooling, by taking heat from indoors and transferring it outdoors; it heats, by taking heat from outdoors and transferring it indoors. For example: blowing 55-degree air across a cold outdoor coil heats up the refrigerant inside the coil. After being squeezed by the compressor, the refrigerant becomes hot enough to warm a house. A fan blows air across a coil with the refrigerant making the air warm enough to provide heating.

In short, rather than removing heat from indoors and dumping it outside like an air conditioning unit, a heat pump finds heat outdoors and dumps it indoors, heating the interior space.

A COLD CONUNDRUM

Heat pumps are an important player in the decarbonization and energy reduction game because they are 3 to 5 times more efficient than electrical resistance heating. Using a heat pump to scavenge heat from the outdoors only requires 20-33% as much electricity as it does to generate the same amount of heat through electrical resistance.

If a nation wants to electrify buildings en masse to mitigate the impacts of climate change, heat pumps look like an obvious winner. But they have a very serious limitation – ordinary heat pumps can only “recruit” heat from outside air when the air is moderately warm. Conventional heat pumps begin losing their ability to collect heat efficiently from outside air at about 40 degrees. Thus, heat pumps are a favorite in the southern US, in warmer climates such as Phoenix, Dallas, and Atlanta.

But a huge portion of the United States has cold winters, with temperatures too low for heat pumps to recruit heat effectively. Some specialized systems can recruit heat at temperatures as low as -10 degrees, but these systems are small and expensive. Most larger commercial heat pumps become unable to heat as the ambient temperature falls.

To avoid being without heat on unusually frigid days, heat pump systems usually include a built-in electric resistance heater as a backup heat source. These resemble those glowing red toaster wires we mentioned earlier. The backup electric resistance heater cycles on when it’s cold to recruit heat from the outside air. Thus, electric-only customers are forced to use the most expensive, energy-intensive form of heating – paying 3 to 5 times the cost per unit of heating – at exactly the time of year when their heating needs are the greatest.

When large numbers of customers use electric heating in cold climates, it can stress the power grid. Bernhard evaluated the consequences of converting a city block’s worth of office and lab buildings from gas to electric resistance heat. The substations providing electricity to the entire city (population 50,000 – 75,000) totaled 22 Megawatts of capacity. Converting just one city block from gas to electric would have exceeded the grid’s limits and required the construction of a new 8-Megawatt substation. Imagine the electrical requirements of converting the entire city.

ONE POTENTIAL SOLUTION: STOCKPILE SUMMER HEAT FOR USE IN WINTER

To find a solution, we explored a very ambitious idea: could we capture summer heat and store it until winter?

First, we needed to know how much heat would be required. According to our calculations, the amount of heating needed in storage exceeded the amount of heat removed from buildings during the summer by 3 to 7 times – depending on the building. So even if we could store all the heat summer extracted from buildings to keep them cool, we wouldn’t have nearly enough heat to meet the client’s winter heating requirements. We needed a way to collect more heat than a refrigerant cycle could scavenge from building interiors during the summer.

One good option is rooftop solar panels. Rather than using these panels to generate electricity, we would use solar energy to heat water by passing water through a network of black piping that’s exposed to the sun.

An even more effective way of capturing heat during summer months is using fans and coils, blowing hot summer air across water-filled coils. It’s a comparatively cheap system to install and captures 5-10 times as much heat per square foot as the aforementioned solar panels.

With a potential method for obtaining large amounts of heat during the summer, we needed only to store it until winter while not allowing the water to cool off. But where to store it? To keep a gallon or two of water hot for several months without a heating source would require an insulated vessel, like a Thermos bottle. To retain enough energy to heat a large building through the winter though, would require storing hundreds of millions of gallons of water.

The size of the underground storage tank required to store this much water was unfeasibly big. For example, just one building we were studying on the client’s campus would have required the construction of an underground, insulated storage tank 300x300x300 feet. Roughly one and a half football fields in area, and 30 stories deep.

ANOTHER POTENTIAL SOLUTION: PHASE-CHANGING MATERIALS

Such a massive tank was clearly unrealistic. But could we reduce its size? Bernhard next explored Phase Change Materials (PCMs) as a way of reducing the required volume of the heat-storing solution. Phase change materials are able to store energy very efficiently. Ice is the most well-known example of a PCM. Adding an ice cube to your drink cools it much, much more effectively than adding the equivalent amount of cold water.

Ice could be an effective means of storing energy if we could find a large, commercial heat pump rated for temperatures below 32F, the freezing point of water. But at present, such technology is still early in development.

There are other PCMs that change phase at different temperatures, but they’re expensive. In exploring different materials, Bernhard engineers found a European company with a PCM that changes phase at 60F.

Such a material could drastically reduce the amount of space needed to store the required amount of heat. But when Bernhard told the supplier how much of the material we’d need for the project, they asked if we had possibly made a typo in our request – by a factor of 1,000. Buying enough of the 60F PCM to complete the project would have been outlandishly expensive.

ANOTHER POTENTIAL SOLUTION: PULLING HEAT FROM UNDERGROUND AQUIFERS

Another possibility for decarbonized winter heat for our client takes us underground. The city where the client’s campus is located happens to be situated a few hundred feet directly above a vast underground aquifer that spans the width of the entire state.

The water in this aquifer is approximately 60 degrees Fahrenheit year-round. At that temperature (20 degrees above the point where heat pumps can successfully scavenge heat), the aquifer could serve as a source of infinite, recruitable heat for every building on campus in winter and an infinite heat sink in summer.

This solution has actually been utilized already to heat a few buildings in Utah and other states with underground aquifers. It requires some capital investment but drilling holes for piping costs much less than building a new massive water storage tank for each building. There is even one building on our client’s campus that has been using heat pumps to draw heat from the aquifer for several years. It’s a promising strategy for decarbonized cold-climate heating.

However, this solution was deemed unworkable campus-wide for our client because of the long regulatory and oversight process that would have to have been required to make it happen while protecting the irreplaceable aquifer.

CONCLUSION

Despite ruling out storing immense volumes of water as impractical, Bernhard has not given up. We are now exploring other cost-effective ways of storing energy for winter consumption. An obvious option is to pair a solar array with batteries. But another possibility might be a solar-powered hydrogen generator. Hydrogen can be stored until needed for heat. Unlike fossil fuels, which create greenhouse gases when burned, hydrogen creates water. Other possibilities include capturing and storing methane from a nearby landfill and using it as fuel. Burning methane as fuel results in a huge reduction in carbon emissions compared to continuing to let it escape into the atmosphere.

Perhaps one of these will be the answer, or maybe another technology will emerge. For example, Oak Ridge National Labs is exploring technology that works similar to a catalytic converter, allowing natural gas to be burned, but with only a fraction of the emissions. Although not fully ‘net zero,’ such a technology might provide an interim solution until human ingenuity invents something better. It’s an exciting time to be in the energy industry, especially at a company like Bernhard which is at the intersection of implementation and cutting-edge technology.

Bernhard leaves no stone unturned or idea unconsidered when working to find solutions to the issues standing in the way of a client’s decarbonization goals.

So, what are the problems that are holding back your decarbonization goals? Whatever they are, the experts at Bernhard have the tools, technology, talent, and experience to work with you in finding a solution. Ready to learn more? Contact us today.