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March 21, 2023
Is your building using a decentralized or centralized power system? This article will explain why centralized low-voltage DC power systems are bringing buildings into the sustainable future, and reducing project capital costs associated with cable and power supplies.
Chapters:
Decentralized and Centralized Power Generation
Decentralized and Centralized Power Distribution
Centralized Power Systems and AC to DC Conversions
If you’re looking to learn more about centralized power distribution systems in buildings, you’ve come to the right place. Here, we’ll briefly compare centralized and decentralized power generation systems, then move on to compare centralized and decentralized power distribution systems in buildings. For these systems, it’s important to consider where power is being converted from AC (alternating current) to DC (direct current), and how efficient these conversions are. This is especially relevant since about 70% of our power loads these days require DC power. By the end of this article, you’ll know if centralized DC power distribution is right for your building, and why.
When talking about distributed (decentralized) and centralized power systems, it’s common to fall into a discussion on power generation. Power grids typically operate on a macro level, and are centralized. In power generation terms, to be centralized means that power is generated and transmitted from one, central location at a macro level. According to the U.S. Energy Information Administration (EIA), most of the electricity in the U.S. was generated by natural gas, nuclear energy, and coal in 2020. Conversely, at a micro level, a decentralized power system typically utilizes renewable sources to generate power. These systems can be connected to centralized stations, creating power “islands”, or they can operate completely independently of the grid (i.e. microgrids).
Many countries have goals to move away from non-renewable power sources, such as coal, gas and nuclear, and move towards sustainable sources of energy, such as solar (PV) panels, wind turbines and, more recently, nuclear fusion. As we utilize more renewable sources of energy, we are reducing our overall usage of fossil fuels. Decentralized power systems help us do that since decentralized power generation usually implements renewable sources of energy. This is why, as a society, we’re moving towards decentralized power systems when it comes to power generation.
Decentralized power generation can also offer benefits such as:
Moving away from power generation, we can also compare centralized and decentralized power systems with respect to power distribution in buildings.
Consider the light fixtures inside your building; they are each connected to a power source. A fixture could be the first and only power load of a power source, or it could exist in a line of other power loads that share the same power source (i.e. daisy chaining). In the context of a building, a centralized power system acts as a power source for many loads, including many types of LED fixtures, HVAC equipment, 5G distributed antenna networks (DAS) and more.
It’s not only power generation and distribution that can be centralized or decentralized, whenever there is AC (alternating current) electricity powering DC (direct current) loads, there must be a conversion made from AC to DC power for each of those DC loads. These conversions are executed with rectifiers.
In power systems with decentralized power conversions, rectifiers are often incorporated into device drivers, and power conversions are made on an individual level. Let’s take LED fixtures as an example; LEDs require DC power to operate, so in a decentralized system, conversions would be made on an individual level for each fixture. These conversions are usually quite inefficient because device drivers (where rectifiers are located) are often an afterthought for manufacturers. They typically waste about 20% of the energy consumed by a load. Additionally, these decentralized conversions are the default in buildings (today).
A power system with centralized conversions has a rectifier of some kind connected to the electrical panel of a building. The rectifier makes one conversion from AC to DC power, then distributes DC power directly to connected DC loads. A major benefit of a centralized power conversion system is that it eliminates the need for decentralized conversions, thus reducing wasted energy. Ultimately, this makes DC loads up to 20% more efficient, and significantly reduces operating expenses, especially in buildings with a high proportion of DC loads (i.e LED lights). These days, about 70% of loads require DC power, so implementing a centralized conversion power system in a building (especially larger buildings) usually makes a big difference in terms of energy usage.
An example of a centralized power system (with centralized conversions), is the Cence LVDC Panel. It intelligently distributes the correct voltage of DC power to loads that need it.
The diagram below of the Cence LVDC (low-voltage DC) panel demonstrates how a centralized power conversion system works. The rest of this article will cover the features of a centralized power conversion system, using the Cence Power panel as an example.
You can think of a centralized power distribution system as one big phone charger that powers many devices at once. Consider the diagram above where the Cence LVDC panel is labeled as “centralized DC infrastructure”. The panel accepts AC or DC power sources, then distributes DC power to respective loads, making it the central hub of power for this network of loads. For loads that require more than 100W of power, the Cence HVDC (high-voltage DC) panel works in the same way.
1. Simple Maintenance: Drivers are located in one, easy to access, location.
In the Cence panel, there are 8 drivers that are essentially DC-DC converters (or regulators) that provide a constant current, and each of them has 4 channels that provide up to 100W of power. Because they are located inside the Cence panel, it’s easy to execute any necessary maintenance on them. It’s an added bonus if the centralized drivers are “hot swappable” (like in the example of the Cence Panel), because you don’t have to shut off an AC breaker to perform any maintenance. This means you can likely perform maintenance without the need for a licensed electrician (if your jurisdiction allows for it).
2. Reduced Cabling Needs: With the Cence centralized power system, one can daisy chain identical fixtures on a single branch circuit to reduce cable home runs.
Daisy chaining is connecting multiple power loads along the same cable line (electrically, in parallel). If each power load had to be connected to the power source with separate cables (i.e. home runs), this would increase the amount of cable required for the project, as well as the project’s complexity. To explain this further, PCMag.com gives this definition for a cable home run: “A cable that begins at a central distribution point, such as a hub or PBX, and runs to its destination station without connecting to anything else”. As you can see, a major benefit of daisy chaining is that it reduces project capital costs associated with cable because it reduces the number of necessary home runs.
3. Maximized Yield Efficiency: With the Cence centralized power system, one can daisy chain identical fixtures on a single branch circuit to maximize yield efficiency.
Daisy chaining also optimizes yield efficiency. Let me explain. Each driver inside the Cence panel, for example, can provide a total of 100W of power, and has 4 channels with which to distribute this power (for a total of 400W per driver). If the system could not daisy chain, only 4 loads could be powered. This means that the total wattage for each of these loads would have to add up to 400W, in order for the total available power to be used. If daisy chaining were not supported, and drivers were used to power loads that required, let’s say, only 10W, then only 40W of the available 400W could be used. That’s a yield of only 10%. However, with daisy chaining, more loads can be supported, making it possible to utilize all the available power, even when connecting loads with lower wattage requirements. In this way, having the ability to optimize a power system for power available, and quantity of loads, is known as maximizing yield efficiency.
4. Reduces Energy Consumption: Power systems with centralized AC-DC conversions eliminate the need for inefficient load level conversions.
The “backbone” of a power system is typically high-voltage, especially if power must travel further than a few hundred meters. The “last-mile” of a power system (or last few hundred meters) can be low-voltage, but power must be stepped down efficiently to optimize energy usage. When Cence LVDC is involved in a project, it is located at the start of the last-mile segment of a power system, and executes a highly efficient conversion from AC to DC, as well as highly efficient DC-DC conversions (where DC voltage levels are regulated) within the drivers. From there, DC power can be distributed to loads that need it, reducing energy wasted by conversions at the load level (as we discussed before).
The backbone of a power system should be high-voltage because higher voltages reduce line losses along cables, as well as voltage drop.The last-mile segment of a power system distributes lower voltages mainly for safety reasons, but also because many loads don’t require more than 100W. However, because voltages are lower (and therefore more prone to line losses), it’s best to use DC in the last-mile segment because DC power inherently has less line losses along cables than AC power.
To learn more about why less line losses occur in cables distributing higher voltages, or distributing DC power, you can read our blog about line losses, or check out this video.
When considering power generation, as a society we’re moving over to decentralized power systems. This is because (among other benefits) implementing them could significantly reduce our carbon footprint. For example, small modular nuclear reactors (SMnRs) are decentralized, and are gaining popularity because of the potential role they could play in decarbonization.
On the other hand, when it comes to centralized vs. decentralized power distribution systems in buildings, our existing decentralized power systems are actually the problem.
When drivers are decentralized, or distributed throughout a building, AC to DC conversions are made at the load level by inefficient rectifiers. These conversions waste about 20% of power consumed by a load each time it’s powered on. With a centralized power distribution system, on the other hand, one highly efficient AC to DC conversion can be made, and the correct voltages of DC power can be distributed to a network of DC loads in the last-mile of a power system. This eliminates energy wasted by inefficient, load-level drivers, as well as reduces cable costs associated with home runs (in cases where daisy chaining is enabled). Additionally, because DC power suffers less line-losses along cables, it is ideal to utilize it in low-voltage applications, such as in the last-mile of a power system.
Looking for an efficient way to power DC loads, as well as reduce project capital costs associated with cabling? A centralized, DC power distribution system, with daisy chaining enabled, is what you’re looking for. Cence Power provides this.
If you'd like to learn more about Cence LVDC, or contact a DC power specialist, you can do so through our website.
We improve the value of commercial and multifamily buildings with an intelligent DC power distribution system that's pain-free to install. It combines the benefits of low-voltage wiring practices with voltage capabilities of up to 450 Volts DC.
