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Lighting and its impact on greenhouse energy costs

Lights are one of the most important aspects of a greenhouse energy mix. Lighting extends the growing season to overcome seasonal changes that limit production and revenue. Lighting must be managed carefully to ensure the benefits are not offset by increased power costs.

Whether you already have lights or are considering installing them, you need to understand how the electricity requirements impact your budget. The best way to do this is with an energy plan that will help you:

• Understand your rates, usage patterns and total costs.
• Develop strategies to minimize costs.

Understand Your Rates: Understand your electricity rates, and how changes to your lighting technology or lighting acreage will change your rate class. Rates in most jurisdictions have two components:

• Usage-based commodity costs (on a $/kWh basis).
• Demand-based distribution and transmission costs (on a $/kW or $/kVa basis).

How these components are applied vary between regions. In Alberta and British Columbia, an increase in demand in any one month will pull demand-based costs higher throughout the year. In Ontario, demand costs only increase in the lighting months.

Ontario also has Global Adjustment, which is the bulk of expense for most growers. It can be charged in two different ways. Class B customers (those whose yearly peak demand averages less than 500 kW or those who chose not to opt out of the class) have global adjustment billed based on a monthly rate per kWh. Class A customers (those above 500 kW who choose to opt out of Class B) have global adjustment billed based on a fixed percentage, determined by the site’s usage during the five peak hours of the previous year. By strategically modifying how you use lighting, you can influence your total costs. Class A and Class B customers may take different strategies.

Understand Your Energy Usage: The next step is to look at your interval data – the load profile illustration of your hour by hour usage. With an actual load profile (from historic use) or projected (from schedules for new lighting), you can compare your use against hourly rates and estimate what power costs when you are using it most. This helps you more accurately forecast monthly peak demand, usage and costs.

Interval data can flag potential changes in the effectiveness of your lights. Year-over-year comparisons may show declines in peak lighting load, providing an indication of (e.g.) outages that can be proactively addressed through maintenance.

Develop Strategies to Save: Doef’s Greenhouses in Alberta used their knowledge of usage and rates to reduce their annual demand-related costs by six per cent. They delayed the start of their lighting season by two weeks, which avoided incurring charges during an additional billing period. They saved a further five per cent with minor changes to crop rotation and lighting schedules. The changes had little impact on production, but significantly reduced their demand costs. In a different example, a greenhouse grower in Ontario asked their utility to extend their billing period by one week; this enabled an extra seven days of lighting while avoiding charges from higher demand.

For Class A customers in Ontario, tweaking operations to avoid the five peak hours can significantly reduce costs; mistakenly using full lighting load during the peaks can significantly increase costs. Planning ahead is critical.  

A solid understanding of how electricity impacts your energy costs helps you plan to optimize your greenhouse lighting; minimizing costs while maintaining or increasing yield.

This article was supplied by 360 Energy, one of North America’s leading energy services firms.