Project type: Straw boiler to heat 3 acres of greenhouses
Boiler details: 0.995mw straw boiler with heat exchanger
Fuel type: Straw
Site background:
Guy and Wright are a family run business since 1928. Core business producing fantastic British Tomatoes for 9 months of the year at the site in Hertfordshire. Producing on average 750 tonnes of fruit per year in three acres of greenhouses.
Description of problem before installation:
The site runs a large gas boiler 3.5MW heating three dump tanks 100m3 that store hot water for use in the nurseries three acres of greenhouses. Due to the high gas prices the company was receiving very large heating bills. Winter months in the region of £35000.00 a month. With low tomato prices and high gas bills this was proving to be an uneconomical.
Solution:
0.995mw pre-furnace chamber attached to heat exchanger this a batch loading straw boiler. The unit was integrated to the nurseries existing heating layout so possible to use gas boiler as back up if needed. The boiler featured lambda oxygen control to optimize efficiency with programmable furnace and water temperature control. The system was designed to ensure that it qualified for the RHI scheme.
Straw was selected as the fuel of choice as this was already available in the area and can be delivered in with ease on a regular basis.
Benefits to customer:
The unit being installed outside removed the need to build a boiler house resulting in a low cost installation. shorter lead time due to shorter planning process and lower overall cost. Qualification for RHI subsidy.
Below are the financial benefits to Guy and Wright for moving over from gas to straw.
Boiler Capacity 0.995mw X 1,314 (15% of the number of hours in a year and the time we expect the boiler to be operating at full capacity) X 5.1p / kwth (Tier one) = £66,678 per annum for 20 years, index linked for inflation. Any heat generated above this would be paid for at the lower Tier 2 Tariff of 2.1p.
Combined with a significant fuel cost saving by converting to straw, we would expect the likely pay-back to be in the region of 2-3 years depending how much the boiler runs at tier 2 tariff.
RHI subsidy with guaranteed income for 20 years.
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