July 15, 2021 Emiliano Bellini

Swedish-Austrian research group claims to have demonstrated that the combined use of heat pumps (HP) and rooftop photovoltaic generation can be extended in their countries and in Europe by replacing current subsidies with a carbon tax policy .

According to them, the shift from subsidies to taxation may be a feasible and simpler solution than the many incentive programs currently being implemented across Austria. “The Austrian subsidy program for HP and PV systems is different for each state, creating confusion and inconstancy for potential users,” they warned in the document. Technical-economic analysis of a combined heat pump and solar photovoltaic system for multi-family houses: an Austrian case study, Posted in Energy Strategy Opinion.

Through their analysis, which assessed the profitability of the life cycle of the two technologies, the researchers sought to identify the most critical techno-economic parameters for profitability, which was determined by considering the net present value (NPV); the benefit-cost ratio (BCR) which is given by the investment costs, subsidies and prices of natural gas; and the internal rate of return (IRR). The assessment considered both air-to-water heat pumps (AWHP) and ground source heat pumps (GSHP) used for domestic hot water (DHW) and space heating (SH).

Their model also took into account the annual consumption of gas, electricity supplied by the grid and electricity fed into the grid by a south-facing photovoltaic system mounted on a flat roof at an inclination angle of 42 degrees and occupying about 40% of the available roof area. “These inputs are estimates of annual costs, savings and revenues, which depend on the costs of operating and maintaining the heat pump and photovoltaic systems; O&M saved gas heating system; and the price of gas, the price of electricity and the feed-in tariff, ”said the academics. “With the initial investment costs of the heat pumps and photovoltaic panels, the saved costs of the new gas boiler and the energy results described previously, the economic feasibility of replacing the conventional gas system with a heat pump and a The combined PV system was estimated by calculating the net NPV, IRR and BCR. “

The techno-economic assessment has shown, according to the scientists, that lower initial costs for heat pumps and PV can increase the BCR of this combination and, above all, that its profitability is strictly dependent on gas prices. “Parametric analysis shows that BCR is the most sensitive to gas prices, where a modest increase of 17% makes combined heat pump and PV systems considerably more attractive, even without any subsidy,” said the authors of the ‘article. “This increase in the price of gas could be caused by market forces, the introduction of carbon taxes or environmental or geopolitical reasons.”

They also noted that if this increase in gas prices were combined with a decrease in electricity prices, the use of solar-coupled heat pumps could reach unexpected proportions. “A change in the photovoltaic feed-in tariffs did not significantly influence the profitability of the case examined,” they concluded.

The research group was formed by scientists from the Royal Institute of Technology KTH of the Swedish Department of Energy Technology and the Austrian Institute of Technology (AIT).