By Leora Radetsky
The US vertical farming market is projected to reach $3 billion by 2024, exhibiting a compound annual growth rate of over 24 percent, according to a February 2019 report. Another report, by the US Department of Energy’s Office of Energy Efficiency and Renewable Energy, put the annual electricity consumption of US horticultural lighting installations at 5.9 terawatt hours – equal to the annual usage of about 550,000 US households, and projected that to increase 15 to 25 percent annually.
Horticultural lighting comprises the largest percentage of power demand in controlled environment agriculture (CEA) facilities for fruit and vegetable production. A 2019 study by Toronto’s Independent Electricity System Operator (IESO) found, for example, that “a lit vegetable greenhouse consumes 10 times as much electricity as an unlit vegetable greenhouse, with essentially all the additional electricity used for lighting”.
Clearly, getting a handle on facility efficiency, including horticultural lighting, is a must-have if individual states and the US as a whole hope to rein in carbon emissions and meet energy reduction goals. This increase in electricity usage comes as states, provinces, and cities across North America are confronting the impacts of climate change and working to reduce – not grow – greenhouse gas (GHG) emissions from the electrical generation sector. In the US, 23 states and the District of Columbia have adopted specific GHG reduction targets. Massachusetts law, for example, requires the state to reduce GHG emissions by 80 percent below 1990 levels by 2050, and California is under statutory mandate to cut emissions by 40 percent below 1990 levels by 2030.
The good news is there are reliable, third-party lighting and safety standards to help indoor farmers make the leap from old-school lighting to state-of-the-art light-emitting diodes (LEDs) that use a fraction of the electricity and are increasingly effective for growing a variety of crops. Perhaps even better for farmers is the availability of a new industry-wide benchmark for horticultural lighting and a growing list of qualified products that are third-party certified to meet it.
More about the benchmark later – first, it’s useful to walk through the various lighting and safety standards specific to horticultural lighting.
Most lighting fixtures in the North American market go through rigorous inspection by certified labs. The first part of the check is for safety. An official UL safety standard tailored for the unique challenges of the greenhouse environment was recently released (UL 8800, the Standard for Horticultural Lighting Equipment and Systems). This standard and similar safety certifications at other major labs address wiring, environmental conditions, ingress protection, and worker safety related to prolonged photobiological exposure to the eyes and skin. Growers should always ask a lighting fixture manufacturer about safety certification specifically for horticultural environments.
Next on the standards checklist for horticultural lighting fixtures is performance testing. This often happens at the same labs that do safety testing, but is designed to verify efficacy, output, spectrum, and other important performance variables. Commercial labs are certified for specific standards, so that a test on a fixture is repeatable at any other lab certified to the same standard. This performance testing results in a report summarizing items such as photosynthetic photon flux (PPF), input power (watts), photosynthetic flux efficacy (PPE, measured in μmol/J or micromoles of photosynthetic photons per joule of electrical input power), and spectral content (flux per nanometer (nm) between 400 and 700 nm).
Then, there are flux maintenance standards for LEDs (such as IES LM-80 and IES TM-21) that help make sure the photosynthetic light output of LED products degrades at an acceptable rate to make a grower’s investment worthwhile. The testing and calculation methods that go into these standards were painstakingly developed through a consensus of knowledgeable lighting stakeholders. A key difference between general lighting and plant lighting, however, is how flux maintenance is measured and benchmarked – the bar is significantly higher for plants compared to people since their metabolism and growth are dependent on the light spectrum and amount.
Against this backdrop of standards and testing, lighting and related technologies are quickly evolving. For indoor growers, questions abound – from how long a fixture will last and whether a manufacturer’s claims about efficacy are accurate to the effectiveness of various wavelengths for growing particular crops. The tests described above produce a lot of important information, but it takes an informed reader to analyze and use it to select appropriate horticultural lighting. This is where our organization, the DesignLights Consortium (DLC), comes in. Through our Horticultural Lighting Program, the DLC strives to make the process of vetting lighting products easier, freeing up growers to focus on their core business.
Horticultural lighting specification is a relatively recent addition to the DLC’s work. The organization was founded in the early days of LED lighting to help electric utilities compare different lighting factors and reports to inform their energy efficiency rebate/incentive programs for commercial and industrial electric customers. The DLC began serving as a central clearinghouse for setting energy efficiency and other product performance minimum standards, and for evaluating products against those standards. Then and now, lighting products that pass review qualify for an online qualified products list (QPL) that utilities use to quickly and accurately incentivize high-performing products.
Back to the benchmark mentioned earlier, the goal of the DLC’s new minimum performance standards for horticultural light fixtures is to accelerate the adoption of new energy-saving LED fixtures in controlled agriculture environments. To be on the new DLC Horticultural QPL, an LED fixture must have a PPE of 1.9 micro mol/J, which means it will be at least 10 percent more efficacious than the best non-LED alternative – a 1,000-watt double-ended high-pressure sodium (HPS) fixture. It also must have a Q90 of 36,000 hours (the number of hours before the photon flux output depreciates to 90 percent), and its driver and fan (if included) must have a rated life of at least 50,000 hours.
Importantly, every product is listed online in a searchable, filterable database to help growers and controlled environment agriculture facility designers quickly narrow their options. For example, in a retrofit, a grower might know what PPF is needed from each fixture but might also need to stay within a power budget to avoid rewiring circuits. The DLC’s Horticultural QPL can be filtered to quickly find and compare conforming products.
For utilities and horticultural lighting users alike, trusted, third-party verification holds the same value as it does in other industries. It plays a critical role in ensuring the integrity of a growing array of products – providing assurance that an independent party has done the legwork and is vouching that a fixture can do the job and save electricity.
As the IESO study referenced above noted, horticultural lighting standards developed by the DLC, as well as the American Society of Agricultural and Biological Engineers , “should help to build trust between growers and lighting manufacturers and suppliers regarding performance information as LED technology continues to mature”.
Just over a year since it was unveiled, the DLC’s Horticultural QPL contains 58 products from 18 manufacturers, and additional products are reviewed and added regularly. We’re confident this growing roster of third-party certified products is expanding the options for farmers and providing a greater level of assurance about product performance, leading to quicker and wider adoption of advanced, energy efficient horticultural lighting technology.
Leora Radetsky (firstname.lastname@example.org) is Senior Lighting Scientist at the DesignLights Consortium.