A tea estate is not one site but five, spread over hilly ground at the end of a long feeder. How that shapes a solar scheme for the factory, the pumps and the labour lines, and why the connection you build behind decides the economics.
Bangladesh is home to 166 tea gardens, predominantly in the Sylhet and Moulvibazar districts, producing approximately 90 million kg of tea annually. An estate is not one building with one bill. It is a factory, a set of irrigation pumps, several blocks of worker housing and an office, spread across hilly ground, often at the end of a long and weak distribution feeder, and many estates still lean heavily on diesel generators as a result. That geography, more than the size of the load, is what makes an estate solar scheme different from a factory one.
| Energy use | Load | Solar solution |
|---|---|---|
| Tea factory (withering fans, dryers) | 50-200 kW | Rooftop solar on factory shed |
| Irrigation pumps | 10-50 kW | Solar pumping system |
| Worker housing (100-500 units) | 20-100 kW | Rooftop solar on housing blocks |
| Office and management | 5-20 kW | Rooftop solar on office building |
| Diesel generator replacement | Full backup | Hybrid solar and battery |
Over 100,000 permanent workers live on the estates, which is why the housing load is on that list at all and why it behaves differently from the rest: it peaks in the evening, when the array is producing nothing. The factory load, by contrast, is a daytime and shoulder load through the flush. Treating those two as one pool of demand is the commonest sizing error on an estate scheme.
The tea factory is the largest energy consumer on any estate. Withering troughs use large fans that run for 14 to 18 hours during the flush season from March to November. A 200 to 500 kWp rooftop plant on the factory shed can power the withering fans during daylight hours, significantly reducing grid or diesel consumption. The factory's corrugated metal roof is well suited to solar mounting, and clamp-based racking that grips the sheet profile requires no roof penetration.
Two qualifications on that roof. First, a tea factory is a humid building with heat and moisture rising through it, so the underside condition of the sheeting and the state of the fixings need inspecting rather than assuming. Second, factories sit in the middle of the estate, which usually means mature shade trees close by. Tree shading is the one shading source that gets worse every year, so the shadow analysis has to model the trees at their likely future height and the string layout has to be arranged so that a shaded corner does not drag a whole string down.
This is the decision that most affects the return, and it is usually settled before anyone thinks about it. Net-metering nets imported against exported energy on a given connection's bill. An estate with separate connections for the factory, the labour lines and the office cannot use generation from the factory roof to cancel consumption on the housing meter. So the plant behind the factory connection earns its value against factory consumption, and a housing scheme has to stand on housing consumption or on being off-grid with storage.
The related trap is distance. It is tempting to build one large array on the best roof and distribute the power around the estate. On hilly ground with hundreds of metres between buildings, that means low-voltage cable runs where voltage drop, not current rating, sets the conductor size, and the cost of copper rises faster than the saving from a single larger array. Siting a smaller array near each load is almost always the better engineering answer on an estate, even though it looks less efficient on a spreadsheet.
Tea nurseries and young tea sections require regular irrigation, especially during the dry season from November to February. Solar water pumping systems, using DC submersible pumps powered directly by PV panels, remove the need for grid power or diesel for irrigation altogether. A 5 to 10 kWp solar pumping system can replace a 5 HP diesel pump, saving BDT 8,000 to 15,000 per month in fuel costs.
The attraction of direct-coupled pumping on an estate is that it needs no connection, no meter, no utility application and no battery: the pump runs when the sun is up, which is when you want to irrigate anyway. The design work moves instead to the hydraulics, meaning head, borehole depth, delivery distance and storage tank sizing. Get a tank of a sensible size and the system tolerates a cloudy afternoon without anyone noticing.
Many tea garden worker housing blocks in Sylhet and Moulvibazar have limited or unreliable grid connections. Rooftop solar with battery storage on housing blocks provides reliable lighting, fan power and mobile charging, improving living conditions and reducing estate management costs. A 20 to 50 kWp system with 40 to 100 kWh of battery storage can power 50 to 100 housing units.
Housing schemes fail for social reasons more often than technical ones. The load grows: households add fans, televisions and small appliances, and a bank sized against today's usage is flat by the third year. Fit distribution boards with per-block metering or simple load limiters, agree in advance who is responsible for replacing a failed component, and put the batteries somewhere ventilated, secure and reachable for maintenance. None of that is expensive at design stage and all of it is expensive later.
Estates are rural, so grid-connected schemes go to BREB through the local Palli Bidyut Samity, on the SREDA-format application with the single-line diagram, module and inverter datasheets carrying IEC certification numbers, roof plan, a recent bill and the estate's trade documents. Allow for a technical committee review and a site inspection, and allow more calendar time than a Dhaka application would need. Direct-coupled pumping without a grid connection does not need this route at all.