Virtual Grower: Software to Calculate Heating Costs of Greenhouse Production in the United States

Abstract

<jats:p>Greenhouses are used in many climates for season extension or year-round production and can be expensive to heat. Greenhouse users and growers are often faced with management decisions that rely on an understanding of how temperature settings, heating systems, fuel types, and construction decisions influence overall heating costs. There are no easy-to-use programs to calculate heating costs associated with these factors over full cropping seasons. A computer program called Virtual Grower was created that helps calculate heating costs at many U.S. sites. The program uses a weather database of typical hourly temperature, light, and wind information of 230 sites from the National Renewable Energy Laboratory in the calculations. A user can define unique design characteristics such as building material and construction style. The user also defines the type of heating system and heating schedule, and then the program will predict heating costs based on typical weather at the selected location. Shorter-term predictions with weather forecasts of 2 days or less can be made with the software if there is an internet connection through integration with local weather forecasts. Virtual Grower can serve as a platform from which many other features can be added, such as plant growth and scheduling. Continued development will improve the software and allow users to perform baseline analysis of their heating costs, identify areas in their production to improve efficiency, and take some of the guesswork out of energy analysis in unique greenhouses.</jats:p>

The Influence of Day and Night Temperature Fluctuations on Growth and Flowering of Annual Bedding Plants and Greenhouse Heating Cost Predictions

“…Heating cost estimation. The cost to heat a 1991-m 2 greenhouse to produce a flowering crop grown at day/night (16 h/8 h) temperature set points of 18/18, 20/14, 16/22, 22/22, 24/18, or 20/26°C for finish dates of 15 Mar., 15 Apr., or 15 May was estimated for Charlotte, NC, Grand Rapids, MI, and Minneapolis, MN, by using the Virtual Grower 2.51 software (Frantz et al, 2010). Production time for each species was calculated from the greenhouse experiments by using the mean time to flower at an MDT of 18 or 22°C.…”

Elevating Carbon Dioxide in a Commercial Greenhouse Reduced Overall Fuel Carbon Consumption and Production Cost When Used in Combination with Cool Temperatures for Lettuce Production

“…In other words, ventilation would help alleviate CO 2 drawdown, but even in wellventilated greenhouses, CO 2 would still be less than outside conditions. Using Virtual Grower software (Frantz et al, 2010) to simulate the cost of heating between a well-sealed greenhouse as described above to a wellventilated greenhouse with 5.0 air exchanges per hour, the costs of heating in Toledo, OH for December through February rises from $15,147 to $27,436. Clearly, it is more expensive to ventilate for CO 2 control than add supplemental CO 2 .…”

“…Fuel use simulations were performed using Virtual Grower software (Frantz et al, 2010). A previous study (Frantz et al, 2010) evaluated this greenhouse as part of the verification of Virtual Grower's accuracy. Predicted fuel use and cost was found to be within 5.1% to 5.6% of actual costs based on the grower's heating bills.…”

“…A single-bay greenhouse with double polyethylene covering with sizes matching the experimental greenhouses was used as the structure within the Virtual Grower software (Frantz et al, 2010), with Toledo, OH, weather as the weather database. A temperature set point of either constant 62 or 65°F was simulated.…”

“…The objective was to compare lettuce growth within a low-temperature greenhouse supplemented with CO 2 against lettuce growth within a more traditional warm, well-insulated greenhouse, without CO 2 injection. This experiment was combined with simulations using Virtual Grower software (Frantz et al, 2010) that compared cost, fuel use, and C consumed because of heating and CO 2 supplementation between the two greenhouses.…”