That's because concept cars aren't investments. This project is an investment. Investors invest in investments to get a return on their investment (ROI). Car buyers, other than car dealers and outfits like Budget Rent-A-Car, do not buy cars to get ROI. Advertising an investment without publishing any projected ROI figures (the business plan you mention) is like advertising a concept car without publishing any photos, video, or drawings.
And I don't think it's accurate to say, "this is a first-time installation of a new technology that hasn’t scaled". People have been using thermal energy storage for household heating for literally millions of years. https://en.wikipedia.org/wiki/Thermal_mass https://en.wikipedia.org/wiki/Thermal_energy_storage https://en.wikipedia.org/wiki/Storage_heater https://en.wikipedia.org/wiki/Ondol#Advantages_and_disadvant... https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storag... https://en.wikipedia.org/wiki/Masonry_heater https://en.wikipedia.org/wiki/Ground_source_heat_pump https://en.wikipedia.org/wiki/Trombe_wall https://en.wikipedia.org/wiki/Feolite https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community https://en.wikipedia.org/wiki/Kang_bed-stove https://en.wikipedia.org/wiki/Earthship#Thermal_performance https://en.wikipedia.org/wiki/Rocket_mass_heater https://www.helen.fi/en/news/2018/Gigantic-cavern-heat-stora... https://en.wikipedia.org/wiki/Barra_system https://en.wikipedia.org/wiki/Storage_heater https://en.wikipedia.org/wiki/Earth_shelter#Active_and_passi... https://en.wikipedia.org/wiki/Bokpoort_CSP#Energy_storage https://en.wikipedia.org/wiki/Russian_stove#Design https://en.wikipedia.org/wiki/Passive_solar_building_design#... https://en.wikipedia.org/wiki/Aquifer_thermal_energy_storage https://en.wikipedia.org/wiki/Home_energy_storage#Thermal_en... https://en.wikipedia.org/wiki/Qanat#Cooling https://en.wikipedia.org/wiki/Regenerative_heat_exchanger https://en.wikipedia.org/wiki/Rammed_earth#History https://www.mha-net.org/ https://en.wikipedia.org/wiki/Solana_Generating_Station#Ener... https://en.wikipedia.org/wiki/Hot_water_storage_tank