Rooftop Vertical-Axis Wind Turbine

The ask

Manufacture a compact 3 kW vertical-axis wind turbine (VAWT) designed for urban rooftop installation — low-vibration, low-noise, omni-directional — and sell directly to commercial building owners in Chattogram, Cox's Bazar, and coastal factory zones where wind resources complement solar and grid reliability is poor.

Why now

Small VAWT designs have improved substantially in the last five years — helical Darrieus and Savonius-hybrid geometries now achieve 25–35% efficiency at low wind speeds (3–5 m/s) versus 15% for first-generation designs. Chattogram's average rooftop wind speed is estimated at 4.5–5.5 m/s, within the productive range. Net metering regulations in Bangladesh now allow rooftop generation below 200 kW to be credited against bills — a critical enabling policy. Solar-wind hybrid systems reduce battery storage needs by 30–40%, improving the ROI of the full rooftop energy system.

Why Bangladesh

Bangladesh's 710 km coastline exposes Chattogram, Cox's Bazar, Khulna, and Patuakhali to consistent sea breezes that solar panels do not harvest. Grid unreliability at coastal factory clusters (8–14 hours of load-shedding per day during peak summer) makes on-site generation a genuine business-continuity investment, not just an environmental one. The garment sector — which operates large flat-roofed factories — is an obvious anchor customer and has proven willingness to invest in rooftop solar; wind is the next logical add-on.

As a business

A 3 kW unit sold and installed at ৳2–3 lakh per turbine to commercial rooftop customers, with a 5-year maintenance contract at ৳15–25K/year, creates a serviceable recurring revenue base. A factory with 20 turbines is a ৳50–60 lakh installation — the kind of ticket a commercial building contractor can upsell alongside an existing solar contract. Local manufacture (welded steel frame, locally wound generator) keeps the import component below 40% and protects margin from FX volatility.

Economics

Move the sliders to model a VAWT manufacturing and installation business. Defaults are order-of-magnitude estimates — pressure-testing them is part of what a founder pitches us.

What ZEPH would back

A founder with mechanical or electrical engineering chops who has built a working prototype tested on a Chattogram rooftop through one cyclone season, and who has a letter of intent from a factory or hotel willing to buy the first commercial batch. We are sceptical of VAWT businesses that rely on imported turbine heads — local manufacturing capability is a prerequisite for the economics to work in Bangladesh.

Impact

A single 3 kW VAWT at Chittagong's average 5 m/s wind speed generates roughly 6,000–7,000 kWh/yr — avoiding around 5 tCO₂e versus diesel backup or grid power. At 120 units sold per year the annual fleet displacement is ~620 tCO₂e; as the installed base grows to 200+ units the recurring service revenue demonstrates commercial viability while locking in 1,000+ tCO₂e/yr of avoided emissions. Coastal factory clusters importing diesel for generators represent the largest FX savings pool — each displaced diesel kWh saves approximately $0.08 in imported fuel.