DC-Powered Buildings 2024; Great Progress
Greater potential
I usually get a blank stare when I tell customers, partners, and friends that August Berres creates cordless mobile furniture endpoints for DC-powered buildings.
Then I get questions like “What is a “DC-powered building”? “Why does it matter”?
The audience is not always engineers or electrical contractors. Engineers and contractors are quick to grasp the concepts. Most people who need to be convinced about the benefits of a DC-powered building are usually less technical. I try different approaches to explain the benefits of moving away from AC power with limited success.
When they learn they can save 30% on their electricity bill with end-to-end DC power, I have an attentive audience.
The explanation that seems to work best for me is to break the concept of a DC-powered building into three parts. I refer to these as Generation, Distribution, and Endpoints. The image below illustrates my point.
Three Elements of the Smart Building Power Ecosystem
How DC power is created, distributed, and used in a building
Describing the DC-Powered Building Ecosystem
Generation
Microgrids on buildings or their premises can provide behind-the-meter power lowering the cost per kWh. California’s Title 24 rules mandate rooftop generation and provide calculations for the minimum generation and battery storage required on all new buildings of every type.
Meeting the minimum requirements is a start. However, as electricity rates increase in cost, It might be beneficial to go well past the minimum and add additional generation and battery storage. According to some experts, a microgrid may have a large return on investment.
A 2017 study by the California Energy Commission found that the ROI for a small Behind-The-Meter microgrid in PG&E's service area ranged from 6% to 25%. A 2018 study by Sandia National Laboratories found that the ROI for a medium-sized BTM microgrid in PG&E's service area ranged from 11% to 31%. A 2019 study by the Rocky Mountain Institute found that the ROI for a large BTM microgrid in PG&E's service area ranged from 17% to 40%.
The best Microgrid partners offer a Power Purchase Agreement (PPA) for companies with limited capital expenditure capabilities. With a PPA, a third party owns the microgrid. You pay the third party for the power that is generated. This is typically lower than the cost you would pay through a utility. This financial model is not new. It has been widely used in residential solar since the 2000s.
Distribution
In 2022, the National Electrical Code (NEC) published its 2023 edition. This revision includes a new article, Article 726, which defines and regulates Class 4 fault-managed power systems (FMP). This event marks a significant step forward in this innovative technology.
FMP is a power distribution system designed to limit the amount of energy delivered into a fault. This makes them safer than traditional power systems delivering large amounts of energy into a fault, which can cause fires or shocks.
FMP is also more efficient than traditional power systems. They can deliver more power over longer distances with smaller cables. This makes them an excellent choice choice for a variety of applications, including:
Wireless communications: FMP can power wireless routers, antennas, and other devices.
Intelligent buildings: FMP can power sensors, actuators, and other devices used to control building systems.
Controlled environment agriculture (CEA): FMP can power lighting, pumps, and other devices used to grow plants in controlled environments.
The publication of Article 726 in the 2023 NEC is a major development for the electrical industry. It is expected to lead to the wider adoption of FMP and the development of new products and applications.
To clarify, a new category called “Limited Power” is planned for 2026. It will combine Class 2 and Class 4 into a single section in the code to better communicate the requirements.
Endpoints
At the risk of over-generalizing, an “endpoint” is any device found in a building that uses power.
There are many endpoints and many different types of endpoints in a building. Some use small amounts of power, for example; phones, laptops, and tablets. Others consume considerably more power, for instance; motors, pumps, and HVAC systems.
Unfortunately, most endpoints are still designed around AC power. At the same time, many of the AC endpoints convert to DC internally. Since FMP is now part of the National Electrical Code, endpoint manufacturers might see the value of offering a DC power input option.
Some endpoints consume more power than can be provided by the receiver products currently offered by FMP suppliers. In the future, FMP product introductions will deliver more power. Meanwhile, endpoint manufacturers are reducing the power requirements of the endpoints. Expect some convergence between power delivery capabilities and device requirements.
There is progress, particularly with USB-C connections. USB-C connections are gaining traction, especially since the European Union mandated that all devices that use less than 15W be capable of using DC power from a USB-C connection. Currently pending in the California legislature is AB-1659, a bill that harmonizes California law with the European Union mandate.
There is another standard being discussed as well; USB PD 3.1. This will enable a USB connection for devices using up to 240W. There are not yet any rules or laws that require this but we can imagine they are being considered.
USB Connections will be more prevalent in the future
USB PD 3.1 is still in its early stages of adoption. The specification was released in 2021 and allows up to 240W of power delivery over a single USB-C cable. However, a few factors are limiting its widespread adoption:
High cost of compatible cables and chargers: USB-C cables and chargers that support USB PD 3.1 are still relatively expensive. This is because they require special certification and testing to ensure they can handle the higher power levels.
Lack of awareness: Many people are uninformed of USB PD 3.1 and its benefits. This is likely because it is a relatively new technology.
Limited availability of devices that support it: Not many devices on the market support USB PD 3.1. This is likely due to the high cost of implementing the technology.
Despite these challenges, USB PD 3.1 is expected to become more widely adopted in the coming years as the cost of compatible devices decreases and more people become aware of its benefits.
Good Reasons for DC-Powered Buildings
Generation
There are three important value propositions for on-site power generation, also known as a microgrid.
A microgrid results in a lower cost per kilowatt-hour. With AC power, there is a cost to deliver the power to your location. The AC power you use may be generated hundreds of miles away. Getting it to you has a cost in terms of transformers, transmission lines, and local distribution. In addition, there are power losses in the transmission and distribution system. Not every kilowatt distantly generated makes it to your endpoints. It doesn’t matter whether the distant generation is coal, gas, nuclear, wind, or solar. Transmission losses occur no matter the source.
A microgrid battery eliminates peak demand charges. The AC power infrastructure must have the capacity to handle peak demand. This is not inexpensive. For some AC-grid-connected businesses, peak demand charges from their utility might be 20-50% of their electricity bill. In contrast, a well-engineered microgrid uses an on-site battery system with capacity to deal with peak demand.
A microgrid provides resilience. As additional load is added to the AC grid, the frequency of power shutdowns increases, particularly during periods of peak demand. This creates at least a business interruption expense but could also have cost impacts on businesses that rely on refrigeration, kiosks, digital advertising, and self-checkout.
Reasons enough
Each element of a Smart Building Power Ecosystem has strong value propositions.
The Best Reason for DC-Powered Buildings
Solar or Wind solutions produce DC power (the “Source”). The Energy Storage Systems (batteries) store the power as DC. At the other end of the power system, the internal components of most modern devices use DC power for their motors, controls, and circuitry (the “Sink”).
That begs a question about how we move power from the Source to the Sink.
Unfortunately, in today’s world, most electrical designers and contractors default to AC power designs as a matter of habit. They include inverters at the source to create AC power. Since AC power is dangerous, codes, permits, and inspections naturally follow.
If the path from the source to the sink uses DC-to-DC connections, conversions to AC are avoided. Avoiding the conversions can save about 30%. The waste that results from DC-to-AC conversions is heat that must be removed from the building unless you are in a northern climate in the winter.
Save 30% on Electricity
If connections between the elements are DC to DC, about 30% energy savings can be realized.
When Onsite Generation is not possible
There can be instances where on-site generation is not possible.
Many businesses cannot finance the capital expenditure. Other competing capital needs have a higher return and investment capital is limited. A PPA might be an alternative approach but the building owner may not want to make the 15 or 20-year commitment most PPAs require.
Another reason could be the project champion is a tenant, not the building owner. Few tenants are willing to invest in someone else’s building if the building owner is not willing to collaborate.
Many older or historical buildings can be a challenge. Owners may be unwilling or unable to make the necessary structural changes.
In some instances, there is insufficient rooftop or parking lot space to provide an area for a solar installation. One solution is to combine a microgrid with power from a utility.
A microgrid might not be possible
If a microgrid is infeasible, downstream connections can still be DC to DC.
When Endpoints Require AC Power
Championing a new concept like a DC-powered building can be perceived as a risky career move. At August Berres, we encourage our advocates who wish to promote the DC concept to first do small projects “for evaluation”. You can also frame your advocacy as a “pilot project” or a “test site”. Until DC-powered buildings are more widely demonstrated, It is unlikely that you can provide a convincing argument for a high-profile new building.
“Never skip the Beta Test” is a truism we repeat often.
Another point of resistance might be the existing investment in endpoints. For example, if your company bought 200 new AC-powered monitors last year, they are likely to be reluctant to discard these in favor of DC-powered versions no matter what the cost-saving calculations say.
Replacing endpoints just to accommodate DC power also adds “moving parts” to a sales pitch. It is better to keep a project simple.
Some endpoints require more power than can be delivered by the current offerings of fault-managed power; a void in the market. Examples include elevators, escalators, HVAC systems, air compressors, pumps, exhaust fans, and most heavy industrial equipment.
We know that FMP providers are developing higher-wattage systems. We also know that endpoint manufacturers are reducing power requirements. Some are considering FMP products that could provide four times more power than current technology. As these efforts converge, more applications for DC-power will be possible.
Many endpoints use DC power internally but are not engineered for DC power inputs
Some regulatory push might be necessary
August Berres’ Endpoints
August Berres’ endpoints are our battery-powered commercial furniture products. August Berres can fit into any power configuration, AC or DC, as we charge batteries using either AC power (100-220V) or DC power (up to 360V).
August Berres has developed a range of solutions for delivering power to individual work areas without wires or cabling. The battery-powered designs are capable of powering individual work areas, conference tables, and portable monitor displays.
One primary product is a portable battery/USB-C/carrycase product we call C-Power. It is both a standalone product and a basic building block for many of the applications. It features a 200Wh battery and dual USB-C connections. Importantly, it can be paired with a docking system built into furniture to provide power to other devices.
An August Berres C-Power Battery Pack
Used in many August Berres applications, the C-Power Battery Pack delivers DC power to USB-C receptacles when used as a portable source of energy or it can be docked into a product to provide power for devices that don’t yet support USB-C.
August Berres believes that the movement to DC-powered buildings is inevititable. The reasons for going this way numerous and the economic benefits are large not just for building owners but as a matter of public policy as well.
The way forward is not a stark either/or decision between AC and DC-powered buildings. The path to DC power is more nuanced and may require several steps to create a complete DC-powered building ecosystem.
Our present and future product designs are intended to bridge the gaps between an existing AC and future DC environment. The image below highlights some key products and indicates that alternative features for power.
How August Berres adapts to AC or DC power designs
Shown clockwise from the upper left. a 24-position C-Power Charging Cart, a Respond! mobile sit-stand desk, a Campfire education/training Table, and a Juce mobile monitor display system.
