PROPANE-BASED EMERGENCY GENERATORS

Power outages from the grid have become more of a concern to a growing number of people around the country. Some of these concerns are based on an increase in weather-related events like storms, wildfires, or other natural disasters. Other concerns can arise from chronic problems with portions of the grid that need updating or modernization. This can also be the case as more homes are built farther from municipal power lines or where electric power is less reliable or completely unavailable. Either way, there is a need for buildings that are designed to increase the resilience of the people who occupy them and allow them to function safely again in light of these concerns.

Stand-by generators have been used in many commercial and residential buildings for years with the interest of providing emergency power for critical operations in a community. These generators improve resilience by keeping electricity available during a power outage and helping to avoid a loss of critical operations. Such generators can also be the primary electricity source where an “off-grid” solution is needed. Where desired, they can be paired with an on-site solar or wind system to provide electricity beyond the capability or availability of the sun or wind.

When considering the options for powering such an on-site generator, propane generators can be considered based on a number of notable attributes. First, they are normally designed to turn on automatically when the power from the grid is interrupted. Second, they have more advantageous characteristics compared to diesel or gasoline-powered generators. Most notably, propane burns cleaner than diesel and gasoline and a propane-powered generator has been shown to be more reliable than gasoline generators. Third, they run quieter than gasoline or diesel generators - many propane generators operate at less than 60 decibels which is about the volume of a normal conversation.

Selecting propane as the fuel means it can be stored on-site without deteriorating over time. If the rest of the building is using propane for other reasons, then the propane storage tank can be sized to accommodate all of the needs accordingly—a separate storage tank isn’t necessarily required. Overall, propane generators are very straightforward to install and easy to operate and maintain.

Photo courtesy of Propane Education & Research Council

Propane can be used for a full range of hot water needs.

EFFICIENT PROPANE HOT WATER SYSTEMS

Propane can be an efficient means to produce hot water in many residential and commercial settings. In addition to hybrid heating and CHP systems, propane can also be used in a stand-alone domestic hot water system in either of two common ways:

• Propane tank type water heaters: his option has been commonly used to heat water using a gas burner instead of an electric heating element. Typically, propane tank water heaters can use the same connections, space, and venting as natural gas models. Of most interest to building users, propane heats water more efficiently than electricity and can cost up to a third less to operate over time.
• Tankless water heaters: This type of on-demand water heater avoids storing and reheating hot water by eliminating the tank. They operate by quickly heating water in a coil over high-output propane burners, then immediately circulating the heated water through the piping to the plumbing fixtures where it is being called for. By heating water only when needed in this way, it can reduce energy usage by up to 50 percent in some cases. That means the initial investment for a tankless propane water heater is typically offset within three years through lower operating costs. The cost is further reduced in many states that offer a rebate on the installation of propane appliances and by federal tax credits that are available for the installation of most propane tankless water heaters.

Tankless propane water heaters typically last for 20 years or more while tank-type water heaters are known to have a comparatively shorter expected useful life. Relatedly, a tankless propane water heater frees up 93 percent of the space used by a tank-type water heater. Finally, propane tankless water heaters provide an endless supply of hot water that is not restricted by tank capacity. Locating the tankless heater close to the fixtures requiring hot water can also reduce water usage where owners or occupants are “waiting for the hot water to reach the fixture.”

When looking at domestic hot water systems, the best results can be obtained by considering all available options, reviewing propane piping requirements, and verifying the needed controls for the solution selected.

AGRICULTURAL CASE STUDY



Photo courtesy of Propane Education & Research Council

Energy System: Gas Driven Chillers

Application: Indoor Agricultural Facilities

The Challenge: Indoor growing facilities, such as cannabis cultivation is surprisingly energy-intensive─about 10 times as much per square foot as for an office building. Energy is needed not just for the electric lighting to help the plants grow which accounts for up to 30–40 percent of the total energy use. Rather, the largest energy use, often making up 50–60 percent of the demand, is for cooling and dehumidification. That’s because cannabis plants are sensitive to moisture and can grow mildew if the air is too humid. This high energy demand for dehumidification equates to high energy costs for cannabis-growing facilities and may even require expensive and time-consuming electrical infrastructure upgrades.

Energy System Solution: Due to the high electrical cost, some growers are turning to innovative, cost-saving alternative technology: chillers driven by propane or gas. The system uses a propane- or gas-powered engine to drive the compressor in a chiller machine to create chilled water while the waste heat from the engine is recovered to create hot water. Powering these energy-intensive chillers with more affordable propane or natural gas instead of electricity can reduce utility costs by 50 percent, according to manufacturers of this equipment. Perhaps just as importantly, these systems can help growers quickly and affordably retrofit industrial buildings for growing cannabis when the existing electrical infrastructure is insufficient.

Building Example: A cannabis grower in Douglas, Massachusetts, converted an old factory building that made envelopes to more lucrative cannabis cultivation. Many old buildings of this type are electrically constrained and at the mercy of the electrical utility to upgrade. This grower had been told it would take 18 months to 36 months to upgrade the power, but growers don’t have that kind of time to wait. The current situation in the cannabis market is such that in three years, the price is expected to be cut in half. So, time really is money in this business.

Instead, of waiting to upgrade the building’s electrical power capacity, the Douglas grower brought in a gas driven chiller unit that eliminates the need for additional power from the utility. Since the closest natural gas lines were eight miles away, the facility used an existing on-site 30,000-gallon propane tank to fuel the gas driven chiller.

Broader Agricultural Applications: Gas driven chillers have long played a role in institutional buildings such as universities and hospitals for comfort cooling. Its application in agriculture and food and beverage business is foreseen to play a larger role in facilities that use process cooling all the time. Gas driven chillers have a proven track record of running 24/7, 365 days a year with a really high degree of uptime and reliability. That is typically what process-cooling customers really want to see. Cannabis cultivation is leading the way as a smart application for gas-driven chilling because these facilities need cooling year-round. Growers of lettuce, leafy greens, and herbs are also using these types of systems, although their plants aren’t quite as dependent on dehumidification as the cannabis plant.

Resilience Aspects For businesses seeking to enhance resilience, gas-driven chillers can help reduce not only the amount of electrical infrastructure they need but also the size of their backup power generation equipment. Given their intensive energy demand, many cannabis growers are installing 2-megawatt or 4-megawatt generators to protect the crops they’re growing, which may be worth up to $10 million at any given time. By shifting some of the electrical demand to propane or gas, businesses can cut the size of the generator in half, saving millions of dollars by purchasing a more affordable unit.

Environmental Aspects: Powering the chilling with high-efficiency propane can also help to reduce greenhouse gas emissions in many parts of the country where the power grid comes from plants burning fossil fuels such as coal. A hybrid-drive chiller that can run on propane, gas, or grid power has also emerged on the market. While this adds additional resilience by allowing the unit to run on electricity if there’s a fault in the engine, it also allows the operator to choose whether the system runs on propane or electricity based on energy costs or carbon footprint considerations. If the grid electricity becomes 100 percent renewable in the near future, the hybrid unit can switch over to all-electric. If not, then operators have the option to still run it efficiently using propane or gas.

Results: By proving the real-world performance and efficiency of gas-driven chilling, cannabis growers may provide the innovative spark that spreads the cost-saving technology throughout the building industry.

Source: propane.com/2022/06/08/cannabis-growers-are-adopting-an-energy-saving-innovation-bwp/

CONCLUSION

All buildings need energy and owners often look to architects and other design professionals to advise them on the best way to purchase and use that energy. By considering propane systems as a primary, hybrid or secondary energy source, then all options can be reviewed and compared. Based on that, propane is often specified in projects where energy efficiency, resiliency, and reliability are part of the project requirements.

Peter J. Arsenault, FAIA, NCARB, LEED AP is a nationally known architect who has authored nearly 300 continuing education courses focused on advancing building performance through better design. www.pjaarch.com, www.linkedin.com/in/pjaarch