Vila Velebit: kako smo izgradili energetski neutralnu kuću u Lici Villa Velebit: building an energy-neutral home in Lika
Kada su nam Boris i Maja Kovačević iz Otočca opisali svoju viziju — kuća koja ne plaća struju, koja diše sa okolišem, u krajoliku Velebita — znali smo da ovo nije rutinski projekt. Vila Velebit, 380 m² kamene kuće na nadmorskoj visini 650 metara, sada je jedna od najenergijski neovisnijih privatnih rezidencija u Lici. Evo kako smo to napravili.
Opis projekta i lokacijski izazovi
Otočac se nalazi u Gorskoj Hrvatskoj, na rubu Velebitskog kanala — jednom od najvjetrovitijih područja u Europi. Bura ovdje može dostizati brzine i do 200 km/h, što je kritičan faktor za dimenzioniranje nosača panela. Standardni krovni nosači koje koristimo u Primorju ili Slavoniji nisu opcija — zahtijevaju se posebni inox nosači s pojačanim sidrenim sustavima.
Krov vile kombinira dva elementa: jugoistočno orijentirani kosi krov pod kutom 28° (gdje su montirani solarni paneli) i ravni krov nad garažnim dijelom (gdje je projektiran zeleni krov). Nagib terena oko kuće iznosi 12°, što je zahtijevalo posebnu statičku analizu temelja za montažne sustave.
Tehnički sustav: 22 kWp + Powerwall 3
Na kosi krov montirano je 55 panela Longi Hi-MO 7 (400 Wp) u dva stringa, spojenih na Huawei SUN2000-20KTL-M3 trofazni inverter. Zašto Huawei a ne Tesla inverter? Jer je sustav od 22 kWp iznad DC ulaznog ograničenja Powerwall 3 (20 kWp), i zbog trofaznog priključka koji Powerwall 3 ne podržava u punoj mjeri za veće sustave.
Za pohranu energije odabrali smo 2× Huawei LUNA2000-15 kWh — ukupno 30 kWh pohrane, što je dostatno za 36-48 sati autonomije van ljetnih vršnih perioda. Sustav je konfiguriran u "TOU Mode" (Time of Use) koji automatski optimizira punjenje i pražnjenje prema HEP T2 tarifi.
Zeleni krov: 180 m² sedum pokrivača
Ravni krov nad garažom (površina 180 m²) pokriven je ekstenzivnim zelenim krovom s 8 vrsta seduma — od sedum album do sedum spurium. Debljina supstrata je 10 cm, ukupna masa zasićenog sustava (s vodom) iznosi 120 kg/m².
Zeleni krov ima višestruku funkciju: regulira temperaturu potkrovlja zimi i ljeti (smanjuje potrebu za grijanjem i hlađenjem za procijenjenih 15-20%), produžuje vijek trajanja hidroizolacijske membrane (smanjuje temperaturne ekstreme s 80°C na 35°C na površini membrane) i stvara stanište za lokalne insekte i ptice.
„Bura je bila naš najveći protivnik. Proveli smo tri dana u uredu konzultantske kuće za aerodinamiku kako bismo validirali opterećenja panela. Na kraju su nosači dimenzionirani za 1,2 kN/m² tlak vjetra — dvostruko više od standarda za primorsku zonu."
Montaža u rujnu 2025
Montaža je trajala 12 radnih dana u rujnu 2025. Ekipa od 8 tehničara radila je u dva tima paralelno — tim A na solarnim panelima, tim B na zelenom krovu. Instalacija panela zahtijevala je posebnu sigurnosnu opremu zbog nagiba i visine objekta.
Najzahtjevniji dio bila je koordinacija s HEP-om za priključak. Procedura za paralelni rad kućnih elektrana u Gorskoj Hrvatskoj može trajati 4-6 tjedana — angažirali smo ovlaštenog elektroprojektanta koji je pripremio kompletnu tehničku dokumentaciju za HOPS (Hrvatski operator prijenosnog sustava).
Rezultati: tri mjeseca praćenja
Prvih tri mjeseca rada (rujan-studeni 2025.) sustav je pokazao odlične rezultate. U rujnu je sustav generirao 2.680 kWh, od čega je kuća potrošila 890 kWh. Višak od 1.790 kWh dijelom je pohranjen u baterije (630 kWh), a dio injektiran u mrežu (1.160 kWh). Račun za struju za rujan: 8,40 € (fiksna naknada, struje gotovo nula).
U studenom, s kraćim danima i prvim hladnim noćima, samopotrošnja je rasla: 1.240 kWh produkcije, 1.180 kWh potrošnje (grijanje toplinskom pumpom), baterija pokrivala gotovo sve noćne potrebe. Račun za struju: 12,20 €. Cilj energetske neutralnosti — godišnja produkcija ≥ godišnja potrošnja — izgleda ostvariv na godišnjoj razini.
When Boris and Maja Kovačević from Otočac described their vision — a house that pays no electricity bills, that breathes with the environment, in the landscape of Velebit — we knew this was not a routine project. Villa Velebit, a 380 m² stone house at 650 metres altitude, is now one of the most energy-independent private residences in the Lika region. Here's how we did it.
Project description and site challenges
Otočac is located in the Gorski Kotar region of Croatia, on the edge of the Velebit Channel — one of the windiest areas in Europe. The bura wind here can reach speeds of up to 200 km/h, which is a critical factor in dimensioning panel mounting brackets. The standard roof mounts we use on the coast or in Slavonia are not an option — special stainless steel mounts with reinforced anchor systems are required.
The villa's roof combines two elements: a south-east facing pitched roof at 28° (where the solar panels are mounted) and a flat roof over the garage section (where the green roof was designed). The slope of the terrain around the house is 12°, which required a special structural analysis of foundations for the mounting systems.
Technical system: 22 kWp + LUNA2000 storage
The pitched roof was fitted with 55 Longi Hi-MO 7 panels (400 Wp) in two strings, connected to a Huawei SUN2000-20KTL-M3 three-phase inverter. Why Huawei and not Tesla? Because at 22 kWp the system exceeds the DC input limit of Powerwall 3 (20 kWp), and due to the three-phase connection that Powerwall 3 doesn't fully support for larger systems.
For energy storage we chose 2× Huawei LUNA2000-15 kWh — 30 kWh total storage, sufficient for 36-48 hours of autonomy outside summer peak periods. The system is configured in "TOU Mode" (Time of Use), which automatically optimises charging and discharging according to the HEP T2 tariff.
Green roof: 180 m² of sedum cover
The flat roof over the garage (180 m²) is covered with an extensive green roof using 8 sedum varieties — from sedum album to sedum spurium. Substrate depth is 10 cm, total weight when saturated (with water) is 120 kg/m².
The green roof serves multiple functions: it regulates loft temperature in winter and summer (reducing heating and cooling needs by an estimated 15-20%), extends the lifespan of the waterproofing membrane (reducing surface temperature extremes from 80°C to 35°C), and creates habitat for local insects and birds.
"The bura was our biggest adversary. We spent three days at an aerodynamic consultancy to validate panel loads. In the end, the mounts were dimensioned for 1.2 kN/m² wind pressure — twice the standard for the coastal zone."
Installation in September 2025
Installation took 12 working days in September 2025. A team of 8 technicians worked in two parallel teams — Team A on solar panels, Team B on the green roof. Panel installation required special safety equipment due to the roof pitch and building height.
The most demanding part was coordinating with HEP for the grid connection. The procedure for parallel operation of residential power plants in Gorski Kotar can take 4-6 weeks — we engaged a certified electrical engineer who prepared complete technical documentation for HOPS (Croatian Transmission System Operator).
Results: three months of monitoring
The first three months of operation (September-November 2025) showed excellent results. In September the system generated 2,680 kWh, of which the house consumed 890 kWh. The surplus of 1,790 kWh was partly stored in batteries (630 kWh) and partly injected into the grid (1,160 kWh). Electricity bill for September: €8.40 (fixed charge only, virtually zero energy cost).
In November, with shorter days and the first cold nights, self-consumption increased: 1,240 kWh production, 1,180 kWh consumption (heat pump heating), batteries covering almost all overnight needs. Electricity bill: €12.20. The goal of energy neutrality — annual production ≥ annual consumption — looks achievable on an annual basis.