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Energy use: Artificial illumination typically increases energy demand, but reduces heating demand.
Without CHP, the greenhouse has to import a substantial amount of electricity. This electricity is then converted to light, but also to heat. Therefore the heating demand of an illuminated greenhouse is in general lower than that of a non-illuminated greenhouse. The decrement is however less than one might expect, which is caused by the fact that a crop requires a higher average greenhouse temperature when there is more light available for growth.CO2 footprint: The use of CHP-engines typically increase increases the CO2 footprint of the greenhouse.
CHP-engines typically uses use natural gas, the . The CO2-emission associated with the electricity use of an illuminated greenhouse with CHP will be substantially higher compared to a non-illuminated greenhouse.
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The configuration differences between the scenarios are shown in the table below.
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Detailed results
The simulation results are grouped into realized climate, CO2, electricity and heat. Expand each topic for detailed results.
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Illumination featuring LEDs produces less heat than HPS at the same illumination intensity, due to their higher efficiency. This results in a higher heat demand and therefore a higher boiler operation and CHP operation. In scenarios both CHP Scenarios (1.4 and -1.5) the CHP produces a substantial amount of the heat demand, with two valuable byproducts: electricity and CO2.     |
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In the table below the consumption of different sources resources is compared.
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Performance
The overall performance is , expressed in terms of economical feasibility some key numbers and sustainability and , is compared in the Table table below.
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Illumination increases energy demand
The greenhouse without illumination naturally has the lowest energy costs, but has also a substantial lower production. The lower production will have a detrimental impact on the financial feasibility.LED illumination has lower energy demand than HPS
When comparing the illuminated greenhouses, the cases with LED lighting clearly have lower costs than the greenhouses with HPS lighting. This benefit is to be expected, but has to be weighed against the higher initial investments for LEDs compared with HPS-lamps to determine the financial feasibility.CHP decreases costs but increases CO2 emissions
Under the assumed economical conditions, options with CHP lead to lower costs, but higher CO2 emissions.
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Conclusions
Scenario with lowest energy use
Scenario 1.1 with no illumination :
No artificial illumination logically requires the lowest energy use(1.1). Using illumination increases both energy use, variable costs and crop production significantly. When artificial illumination is applied LEDs result in the lowest energy use (1.3).Scenario with lowest CO2 emissions in future energy net:
Scenario 1.2 (HPS without CHP) has the highest electricity consumption, but the lowest CO2 emissions. In these scenarios it was assumed that the electricity from the grid stems from renewable sources. If the average CO2 emission of electricity in the public grid of the Netherlands (350 gram per kWh in the early 2020s) is assumed, the Scenario 1.2 becomes the greenhouse with the highest CO2-emission: 51.5+234.6 x 0.350 = 134 kg/(m² yr). The dominant share of emissions is then produced elsewhere.Scenarios with lowest CO2 emissions in current energy net:
Assigning this 350 gram CO2 - emission to public grid electricity would mean that the CO2 emission associated with Scenario 1.4 would increase with 87.1 x 0.35 = 20 kg/(m² yr), whereas the CO2 emissions associated with Scenario 1.5 would decrease by 32.7 x 0.35=11.4 kg/(m² yr).
This shows that LEDs always outperform HPS lighting.
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