If Colorado’s experience is any indication, energy use is expected to spike with the recent legalization of recreational marijuana in California, much as it did when data centers sprang up throughout the state.
For example, just two years after Colorado legalized recreational marijuana in 2012, grow houses consumed about 2 percent of the power supply in Denver alone.
According to a 2012 study by the California Public Utilities Commission (CPUC), conducted when medical cannabis was legal in California but recreational cannabis was still prohibited, indoor cannabis cultivation is responsible for about 3 percent of California’s electricity consumption, which is equivalent to the electricity consumption of one million California homes.
The cannabis industry has not benefitted from publicly funded agricultural research on how to best optimize production across a variety of cultivation methods, unlike other valuable agricultural commodities in the state.
Additionally, the CPUC finds that what is energy-efficient for one industry may not be energy-efficient for another industry. For indoor cannabis cultivation, for example, insulation requirements may increase cooling needs, and HVAC economizers may increase the need for dehumidification and air filtration
However, the available data are not sufficiently robust to support specific policy recommendations, according to the CPUC. It’s Policy and Planning Division recommends engagement with the cannabis industry, California regulators, utility companies, local jurisdictions, and other stakeholders to explore options for ensuring that California cannabis cultivation is energy-efficient.
But there has been some studies in California about the issue. In anticipation of this new demand, a team of researchers from the Western Cooling Efficiency Center at University of California-Davis lab-tested equipment designed to reduce the energy demand of this rising new industry in the state.
The Western Cooling Efficiency Center was established along-side the UC-Davis Energy Efficiency Center in 2007 through a grant from the California Clean Energy Fund and in partnership with California Energy Commission Public Interest Energy Research Program. The center partners with industry stakeholders to advance cooling-technology innovation by applying technologies and programs that reduce energy, water consumption and peak electricity demand associated with cooling in the western U.S.
Indoor grow houses for cannabis cultivation have unique design considerations, yet state standards and best practices for facility design are lacking. Grow houses often feature multiple, portable dehumidifiers. While these systems remove water from the room, they also create additional heat. Separate, additional air conditioning is then needed to remove the excess heat, making for a power-hungry, inefficient growing process.
The researchers developed a model of a typical grow house and tested a new dehumidifier built by the New York-based company MSP Technology. The scientists found the system could save 30 to 65 percent of the energy a grow house uses for dehumidification and cooling. It also reuses 100 percent of the water it removes from the air to water plants.
Traditional dehumidifiers remove moisture by cooling the air below the dewpoint using an evaporator coil, resulting in cold, dry air. The cold, dry air is then re-heated as it passes over the condenser coil, supplying warm, dry air to the space. The net result is an addition of heat into the conditioned space. This requires another air conditioning unit to be installed to remove both the heat from the lights and the heat from the dehumidifier.
The MSP dehumidifier combines a plate heat exchanger, evaporator coil and a small, outdoor condensing unit. This technology brings in (1) moist return air through a (2) plate heat exchanger to initially cool the return air. This allows the evaporator coil to focus most of its energy on dehumidification, instead of both cooling and de-humidication like a traditional dehumidifier.
The cool dry air then passes back through the plate heat exchanger to reduce the temperature of the incoming moist return air and pick up some of the heat as it is then reintroduced into the conditioned space.
The heat absorbed by the evaporator coil and from the compressor is rejected outside. The net result is dry air delivered to the space with a small reduction in temperature, which counteracts the heat from the lights. A building conditioning system for heating and cooling is then used to make minor adjustments to space temperature as needed.
“The technology we tested is one potential solution but not the only solution,” said Theresa Pistochini, senior engineer at the Western Cooling Efficiency Center at UC Davis. “We need to acknowledge this as a legitimate engineering problem that needs to be solved.”
“We want to start creating best practices for this industry as it develops,” Pistochini said. “It’s hard to retrofit after the fact. It’s better to build it right the first time. There are solutions out there if one goes looking.”
California officials are looking into other solutions. According to a CPUC workshop report “Energy Impacts of Cannabis Cultivation” in April, due to the correlation between license type and on-site energy use, the availability of indoor and mixed-light licenses across localities could provide utility planners with valuable information on load growth potentials attributable to commercial cannabis cultivation.
Hezekiah Allen, the executive director for the California Cultivators Association, emphasized that, unlike other states that have legalized commercial cannabis cultivation, California utilities and regulators will have better data access to ascertain and respond to any potential energy impact of cannabis cultivation due to the inherent structure of the state’s regulatory framework.
He further emphasized that the electricity demand spikes experienced by states such as Washington and Colorado are not likely be replicated in California due to limited license availability and California’s higher electricity rates. “California is a not a cheap electricity market. California is not going to cost competitive at a large-scale with indoor cultivation only,” Allen said. “Impacts can be allocated based on the [cannabis] regulatory structure.”
CalCannabis and the California Department of Food and Agriculture recently released a statewide programmatic environmental impact report (PEIR) under California Environmental Quality Act (CEQA) to understand and mitigate the statewide effects of cannabis cultivation.