Energy management · Building simulation · Sustainable tourism · Finland
Techno-economic scenario modelling for a sustainable tourist resort on Hylkysaari Island near Helsinki, using IDA ICE building simulation, HOMER PRO microgrid optimisation and Excel economic analysis, in collaboration with Valo Finland.
Evidence dashboard
Which sustainability pathway gives Hylkysaari the best balance between energy demand reduction, renewable supply, waste-heat recovery and economic viability under Finnish island constraints?
IDA ICE generated building energy demand for each scenario, HOMER Pro optimised the island energy system and spreadsheet economics evaluated waste-heat recovery, NPV, benefit-cost ratio and discounted payback.
The strongest recommendation was a hybrid: retain the PV-heavy Scenario 1 economics while taking deeper insulation and expanded waste-heat recovery ideas from Scenario 2.
Annual thermal demand: BAU 939.17 MWhth, Scenario 1 659.22 MWhth, Scenario 2 345.86 MWhth.
Solar thermal economics are sensitive to collector cost, climate assumptions and operating schedules. The project is valuable as a coupled modelling exercise: building demand, local generation, waste heat and investment logic are compared in one decision frame.
Hylkysaari is a 40,000 m² island in the Gulf of Finland, connected to Korkeasaari Zoo by two land bridges. Valo Finland purchased it to transform it into a sustainable tourist destination opening in 2030, with 40 new lodges, a hotel extension, restaurant, public sauna, pool house and event spaces – roughly 1,000 m² of new floor area on a site with close to zero current activity.
Tourism accounts for about 8% of global carbon emissions. Hotels in particular are intensive energy users: European hotels average 200–400 kWh/m²/year and generate 160–200 kg CO&sub2;/m². Finland’s cold climate (-20°C winters) makes heating the dominant load. Hylkysaari’s island geography adds further constraints: construction logistics are difficult, and grid connection resilience matters because external help during an outage is slow.
The research question was: which of three proposed pathways is the most techno-economically optimal for Hylkysaari, with respect to energy efficiency and sustainability?
Each scenario is named after a Finnish wildflower to reflect its ambition level:
IDA ICE modelled energy and heating demand for every building in every scenario. Each building was constructed in 3D from the provided floor plans. Parameters changed between scenarios were wall/roof insulation thickness, window type, lighting wattage, occupancy schedule savings factor, solar collector area and thermal storage volume. The simulation output hourly demand data that fed directly into HOMER PRO.
HOMER PRO received the hourly electrical and thermal load from IDA ICE and optimised the island microgrid. The grid was modelled with an emissions factor of 25 gCO&sub2;/kWh, power price of €0.24/kWh and sell-back of €0.10/kWh. District heating was approximated as a generic boiler at €90/MWh. Solar PV was sized across a search space of 0–400 kW with capital cost of €916.60/kW. Project lifetime 20 years, discount rate 6%, inflation 2%.
Excel handled waste heat recovery calculations and the full economic evaluation (NPV, BCR, DPP). Waste heat sources were the restaurant kitchen (dishwasher at 61°C and cooking exhaust at 70°C), hotel laundry (washer at 60°C and dryer at 90°C) and public sauna exhaust air at 80°C. A standard Q = VρcΔT heat exchanger model was used, with a 50°C return temperature throughout. The dryer contribution was taken as 40% of dryer energy consumption.
The laundry washer alone contributes 79.4 MWh/year and the dryer 31.2 MWh/year. The restaurant kitchen dishwasher adds 18.9 MWh/year and cooking exhaust 37.1 MWh/year. The public sauna, while a symbolically important source, contributes only 0.5 MWh/year due to its intermittent use. Scenario 2 captures all sources; Scenario 1 excludes the kitchen.
The table below summarises the modelled outcomes across all three scenarios:
Scenario 1 (Golden Marguerite) cuts electricity demand nearly in half versus BAU (183.52 vs 324.98 MWhel/year), primarily through LED lighting and occupancy sensors. Solar PV pushes the renewable electricity share from the grid baseline of 55% up to 81.1%. Thermal demand falls by 280 MWhth/year from improved insulation. Waste heat recovery captures 111.13 MWhth/year — 14.4% of annual thermal demand.
Scenario 2 (Fireweed) achieves the lowest thermal demand at 345.86 MWhth/year (versus 939.17 in BAU), driven by further insulation improvement and solar thermal collectors raising thermal renewable share to 33.5%. Waste heat recovery from the kitchen addition brings total recovery to 167.08 MWhth/year — 35% of annual thermal demand. Electricity demand is slightly higher than Scenario 1 (187.41 MWhel/year) due to auxiliary collector components.
Golden Marguerite’s strong economics are driven by grid sell-back during peak PV production hours: with 400 kW installed (the HOMER PRO optimal), the scenario generates income that yields a BCR of 2.21 and pays back the €384k investment in 6.5 years. The solar PV capital cost of €916.60/kW is the single largest cost driver for Scenario 1.
Fireweed’s poor economics stem from the solar thermal collectors (€394.8k of the €546k total CAPEX). The thermal savings from replacing district heating with solar heat are insufficient in Helsinki’s cold, low-irradiance climate to cover that investment. DPP equals the 20-year project lifetime, meaning break-even only at the very end. The BCR of 1.0 confirms the investment is at the margin of viability.
Sensitivity analysis confirmed that Golden Marguerite’s NPC tracks directly with grid power price (higher prices improve the case), inversely with discount rate, and proportionally with PV capital cost — though even under pessimistic assumptions it outperforms Scenario 2.
No single scenario dominates all three KPIs. The recommended hybrid approach takes the solar PV from Scenario 1 (best for KPI 2 — 81.1% renewable electricity) and the deeper insulation, thermal storage and kitchen heat recovery from Scenario 2 (best for KPI 1 and KPI 3). This retains the economically sound PV investment while maximising energy demand reduction and waste heat capture across all three heat-intensive sources (laundry, sauna, kitchen). Solar thermal collectors are excluded on economic grounds.
My contribution to the project was designing the guest-facing business model built around the island’s energy strategy. The Vihreä Program has two pillars:
Target customer segments are environmentally conscious leisure travellers and corporate sustainability programs seeking credible destination partnerships. Revenue streams span premium sustainability-oriented bookings and the offset scheme. The cost structure is dominated by dashboard development, maintenance and offset verification infrastructure.
Relevance
This project sits at the intersection of building energy simulation, renewable microgrid design, economic evaluation and guest-facing sustainability communication. The multi-tool workflow – IDA ICE for buildings, HOMER PRO for the microgrid, Excel for economics – mirrors real consultant and developer practice for small-scale sustainable infrastructure projects.
Designing the Vihreä Program added a dimension beyond technical analysis: translating an energy engineering result into a business model that makes sustainability tangible and commercially viable for the client. That combination of technical rigour and commercial framing is what makes the project relevant beyond academia.