innovation

Are electric heat pumps a cost-effective solution for greenhouses? That was the focus of vegetablesWA-run feasibility studies at three WA farms.

Words Katrina Hill, vegetablesWA RDO

Zeke Zalsman (right) and farm manager Brad. Read Zeke’s review from p16.

Photography

Frances Andrijich

WHEN Zeke Zalsman approached vegetablesWA for funding to help with investigating the feasibility of heat pumps in greenhouses for their Zaldeesh Farms, the innovative idea became a project funded by the VegNET Innovation Fund. The project was expanded to not only include the feasibility of switching their LPG heating system to an electric heat pump, but also two other greenhouse sites – one which currently uses a biomass boiler, which burns agricultural green waste, and another without a heating system installed.

The vegetablesWA project was started by former-RDO Michael Bartholemew. He worked with Zeke (capsicums) and I (RDO Katrina Hill) identified and approached two additional growers – Grown Smart Produce (no heating system, cucumbers) and Stakehill Hydroponics (biomass boiler, tomatoes) to be part of the study. vegetablesWA engaged the Australian Alliance for Energy Productivity (A2EP) to deliver the three feasibility studies, with consultants Deta Global and Energy Smart Water (ESW).

A2EP evaluated and assessed each farm’s existing operating situation and proposed a solution for implementing heat pumps with the associated costs, benefits and risks to each site. Across the three sites, the project found:

• An air-source electric heat pump is capable of providing the required site heat load

• Heat pumps are significantly more energyefficient and cost-effective, promoting optimal plant growth and minimising heat loss

• The heat pump systems proposed were challenging financially due to a range of factors, including high capital expenditure (CAPEX) compared to the added benefit.

So why did the heat pump concept warrant an industry-led study? Providing the right climate within greenhouses is essential to maximising yield, decreasing disease and increasing revenue, however it requires a large amount of energy and potentially carbon emissions. Ideally a greenhouse should maintain an ambient air temperature of 18-19°C and the root level of the soil should maintain a minimum of 20-21°C. This temperature range is crucial for successful yields over winter months.

Greenhouse heating is expected to lead to an increase in the size and quantity of production. This can address market demand in winter months, which is usually underserved. A heating system also allows a grower to maintain summer varietals and produce sizes over cooler/winter periods with potential yield improvements of 25 to 50 per cent and reduced pest pressure. Using heating can add 30 per cent to revenue through increased year-round yields.

Zeke has been impressed by the heat pump performance and its production benefits.

All three sites indicated that heating had the potential to increase revenue. See breakdown of how each conversion is expected to perform:

• Energy consumption reduced by 51 per cent

• Energy costs reduced by $18,200

• Saving of 440 tCO2e per year

• Net present value (NPV) of -$44,900 over 15 years based on capital budgets

• Unfavourable simple payback of 12 years (based on the relatively high costs of electricity [$0.201/kWh] when compared to LPG [$0.137/kWh], low utilisation outside of winter months and high capital costs).

• More energy-efficient and less labour intensive

• Energy savings of 2,550,000 kWh/year due to the coefficient of performance (COP)

• Increase in CO2emissions by 2925 tCO2e per year

• 360kWp photovoltaic system, costing $620,000, was recommended after consultation

• Increase in CO2e missions (currently zero).

• NPV of -$1,156,000 over 20 years

• While energy consumption is expected to decrease by 80 per cent, higher electricity costs relative to biomass will result in the total energy cost increasing from $122,000 to $169,000.

• Economically challenging (due to high supply and installation costs and current low costs of fuel)

• Negative NPV existed with a payback in 9.4 years (low sell scenario); a positive NPV was proposed with a payback in 4.8 years (high sell scenario). Note: further risk analysis and detailed feedback from participating businesses should be conducted to inform the investment decision-making process.

• Air-sourced heat pump system adds to yield and revenue, but increases operating costs and emissions unless using a power purchase agreement (PPA).

So what are the project outcomes and challenges to overcome? Overall, implementing air-sourced heat pumps for root zone heating offers a promising solution to improve yields, reduce costs and minimise environmental impact. It has a low installation complexity when compared to other heat pump options and comparatively low capital costs when compared to ground source heat pumps. The lower electrical capacity required reduces capital costs when compared to direct electric heating and, with the high winter temperatures in Perth, air-sourced heat pumps suit the application.

Although the base scenario in each project represented a negative NPV at this time, several variables have been identified that would warrant re-evaluation. This could progress into a detailed design to provide an economical NPV and internal rate of return (IRR). Economic factors to consider are:

Zaldeesh Farms.

• Changes to LPG, biomass fuel and electricity pricing

• Reduction to heat pump CAPEX – increased market access and pricing

• Government incentives or grants

• Existing heating equipment reaching end-of-service life and requiring replacement

• Further inquiry and estimation of the increased yields and low/high sell scenarios

• Extension to required heating in shoulder seasons and increased greenhouse temperatures.

The feasibility study demonstrates the potential for energy-efficient and sustainable heating systems in the vegetable-growing sector. It identified the potential to increase yield by almost three times with heating during winter. This would be achieved by growing larger-sized summer variants with better production that command higher pricing due to a winter shortage.

Participating growers have now begun a pilot project with another vegetable production business. Zaldeesh Farms has installed further heat pumps (see p16). Grown Smart Produce, in Carabooda, has commenced a full metering study to verify and improve modelling of its heating demands. The study involves the design, supply and installation of: hydronic pipework; heat pump and thermal storage, and control and monitoring equipment. Demonstrations, workshops, training and extension activities will be facilitated by VegNET and vegetablesWA.

For more information, contact RDO Katrina Hill on 0427 373 037 or email katrina.hill@vegetableswa.com.au. Listen to the Heat Pump Feasibility Study Webinar at https://youtube/1g7ovvMv8hk. If you are considering a heat pump installation, visit www.heatpumpestimator.com/.

What’s the difference between space heating and near-root heating? Both systems were modelled to compare energy usage. The study found that in most situations it can be determined that root heating is considerably more efficient than space heating. Key benefits for root heating over space heating are:

• Root heating focuses heat where it is most needed, promoting optimal plant growth

• Root heating reduces heat loss by targeting the root zone, minimising heat loss through the walls of the greenhouse

• As a result, root heating requires lower energy input compared to space heating, leading to cost savings, a smaller equipment footprint and lower CO2 emissions

• Root heating has fewer adverse effects on the humidity within the greenhouse, saving water and increasing plant health.

At one study site, it was found that root heating is about 68 per cent more energy efficient than space heating when comparing space heating duty load and root heating duty load over a standard cold winter day.

vegetablesWA RDO Chi Nguyen learns about Zeke’s production and management.