Power Box — Off-Grid Power for Equipment That Sits Where the Grid Does Not

Every site has equipment that matters and sits somewhere awkward. A PTZ camera at the far corner of a tank farm. A flow computer on a pipeline right-of-way. A repeater on a ridge. A water-level sensor in a canal. A traffic counter on a rural highway. None of them draw much power — typically 10 to 100 watts — and none of them are anywhere near a mains connection.

The three usual answers each fail in a different way. A small diesel generator runs dry in days, needs servicing, makes noise and exhaust, and is the first thing that walks off site. Solar alone has to be sized for the worst week of the year, which in Thailand is a week of monsoon cloud, so both the array and the battery bank end up enormous. Batteries alone mean a truck, a driver and a swap every few weeks, forever.

A Power Box is SATU’s packaged fourth answer, built on EFOY® direct-methanol fuel cells from SFC Energy AG of Brunnthal, Germany.

What is in the box

A Power Box is one weatherproof enclosure containing four things, wired and commissioned together:

• an EFOY® direct-methanol fuel cell — the charger
• a battery — lead-gel, AGM or LiFePO₄ — which actually carries the load
• a solar charge controller, and usually a panel, so PV does the work whenever there is sun
• the methanol fuel, in sealed cartridges inside the same enclosure

The fuel cell does not run the load. It watches the battery. When the battery falls to a set voltage — at night, under cloud, after a long grey stretch of monsoon — the fuel cell starts on its own, charges the battery back up and shuts down again. Nobody presses anything. There is no pull cord, no starter battery, no oil change and no 250-hour service.

That is the whole idea: the solar array is sized for an average week rather than the worst week, the battery is sized for a night rather than a fortnight, and the fuel cell covers the gap between them with a fuel that keeps indefinitely in a sealed cartridge.

Why methanol, and not something else

Energy density is the entire argument. To store and deliver the same amount of energy at a remote site:

One M10 cartridge is ten litres and 8.4 kg, and holds 11.1 kWh. Roughly 280 kg of lead-gel battery would be needed to store the same energy. That ratio is why one person can carry a month of power up a hill, and why a cartridge change is a two-minute job rather than a crane lift.

Methanol is also liquid at ambient temperature and pressure. It needs no compression, no cryogenics and no pressure vessel — which is what separates it from hydrogen at this power level.

Choosing the size

The EFOY® methanol range covers the band where unmanned equipment actually lives. Output figures are at 12 V and 20 °C, and fall gradually with operating hours.

Units can be clustered: the Pro 900 to 2800 class up to 500 W, the EFOY 80 and 150 up to 300 W, the Pro 12000 Duo up to 3 kW. Above that the answer is hydrogen rather than methanol, and we would specify the EFOY® Hydrogen line instead.

Choosing the enclosure

The same fuel cell goes into different boxes depending on whether the site is portable, mobile or fixed. Every enclosure is rated −20 to +50 °C, has deep-discharge protection, air ducting, active ventilation above +35 °C and a built-in solar charge controller.

How long between site visits

Autonomy is a fuel question, and methanol consumption is a flat 0.9 litres per kWh across the range. The fuel manager then decides how many cartridges the unit can reach before anyone has to drive out.

Worked example, an EFOY Pro 1800 holding a 50 W average load with no solar contribution at all: one M28 cartridge gives 26 days. Add a Fuel Manager FM2 and two cartridges give 52 days; an FM4 gives 104 days; an FM8 gives 208 days — nearly seven months without anyone going near the site. With a solar panel in the loop, the fuel cell only runs on the days the panel cannot cope, and those figures stretch considerably further.

A fuel cartridge sensor raises a pre-alarm well before a cartridge runs dry, so a refill is scheduled rather than discovered.

What it tells you, from where you are

An unattended power supply is only as good as its reporting. EFOY® units expose:

• EFOY Cloud — secured MQTT over Ethernet: live status, history, fuel level, e-mail alarms, remote configuration and automatic firmware updates
• Modbus TCP and a clear-text serial protocol, so the box appears on an existing SCADA or building-management system rather than as a separate island
• Local control — an operating panel on the unit, or Bluetooth to the EFOY app for a technician standing next to it
• MultiSense extra channels, so site sensors can be read back over the same link

Where we deploy it in Thailand

SATU’s appointment with SFC Energy covers Thailand across seven industrial segments, and those segments are a fair description of where a Power Box earns its place:

• Security — rapid-deploy CCTV, camera masts, perimeter towers and video trailers on sites with no mains at the fence line
• Traffic — counters, radar, road-weather stations and temporary signal control on rural and interurban routes
• Rail — level crossings, lineside equipment and trackside monitoring away from the traction supply
• Remote sensing — water level, rainfall, air quality, noise, seismic and weather masts that must report through the rainy season
• Telecommunications — repeaters, transmitters and digital radio sites, and extended backup where a site must survive a long outage
• Oil and gas — SCADA and telemetry, valve actuation, leak detection and cathodic protection along a pipeline right-of-way
• Special-purpose vehicles — survey, broadcast, command and mobile-laboratory bodies that must run their payload with the engine off

Fuel: shipping, storing and handling

Methanol arrives in sealed, single-use EFOY® cartridges rather than as bulk liquid, and that is what makes the logistics manageable. M5, M10 and M28 ship as UN 3473, fuel cell cartridges, class 3; the MT60 tank ships as UN 1230, methanol, class 3 (6.1), packing group II. All are UN-approved for sea, road and air transport, and every filling is supervised by SFC quality management.

Cartridges store and operate between −20 and +50 °C. The M10 is stored and used upright; the M28 may lie on its side provided the valve faces upwards. SATU handles import, cartridge stock and scheduled replenishment in Thailand, so the site sees a delivery rather than a customs problem.

What a Power Box is not

It is worth being plain about the limits, because specifying one of these against the wrong duty wastes everybody’s time.

• It is not a generator. A single methanol unit delivers 40 to 500 W. If a pump, a compressor or an air conditioner has to start, this is the wrong product — that is a hydrogen system or a genset.
• It is not a UPS. The fuel cell charges a battery; the battery carries the load. Ride-through is a battery sizing decision, not a fuel cell one.
• It does not make cold. Nothing in the box air-conditions a cabinet.
• The exhaust must go somewhere. The products are water vapour and carbon dioxide, but inside an enclosed space the off-gas still has to be ducted outside.
• It needs above +3 °C to start. Never a constraint in Thailand, but it is a real number and we would rather state it.
• Fuel is a consumable. The running cost is cartridges. Where mains power is available and reliable, mains wins on cost every time.

What SATU supplies

SATU Innovative is SFC Energy’s authorised distributor for civil products in Thailand. On a Power Box project that means the load survey and sizing, the fuel cell and enclosure selection, the battery and solar hybrid design, commissioning on site, connection into your SCADA or monitoring platform, cartridge supply and scheduled replenishment, and after-sales service. The appointment covers SFC Energy’s civil (non-military) products only.

If you can tell us the average load in watts, the site location and how often somebody is willing to visit, we can size the system and tell you honestly whether a Power Box is the right answer or whether you should simply run a cable.

Common questions

How is this different from a solar-plus-battery system?

It usually includes one. The difference is that the solar array and battery bank are sized for an average week rather than the worst week of the year, because the fuel cell covers the shortfall. That normally makes the whole installation smaller, lighter and cheaper to mount — and it removes the failure mode where a fortnight of monsoon cloud takes the site offline.

What comes out of the exhaust?

Water vapour and carbon dioxide. There is no particulate exhaust and no fuel smell in normal operation, which is why these units are used inside vehicle bodies and equipment rooms with the off-gas ducted out.

How loud is it?

Under 50 dB(A) at one metre for the EFOY Pro 900 to 2800 class, and it only runs part of the time. In practice a running Power Box is quieter than the traffic on the road beside it.

What maintenance does it need?

Cartridge changes, and a service interval measured in thousands of operating hours rather than hundreds. There is no engine oil, no air filter and no fuel polishing.

Can it be stolen?

Anything on a remote site can be stolen. The practical difference is that a Power Box has no resale value as a fuel container and no siphonable diesel in it, and because it reports to EFOY Cloud you learn about an intrusion in minutes rather than on the next site visit.

Does it work through the rainy season?

That is the case it is built for. Solar yield collapses under monsoon cloud; methanol capacity in a sealed cartridge does not change with the weather. The enclosures are rated IP33 or IP54 and to +50 °C.

What if I need more than 500 W?

Cluster the methanol units up to about 3 kW, or move to the EFOY® Hydrogen line, which starts at 2.5 kW and scales to 50 kW, and to 200 kW in the H2PowerPack class. We will say which one fits rather than stretching the methanol range past where it belongs.

Related

• Methanol fuel cells for unmanned sites: seven applications, one architecture
• SFC Energy — EFOY® fuel cells
• All SATU solutions
• Tell us about your site