Solving the energy problem for the Covid-19 homeworker in an off-grid enviorment

Over the next few weeks, I am going to be focusing on technical topics which can may assist the aid sector in our fight against COVID-19. So let me kick off this series of articles by addressing one important issue that affects aid workers living in the “Global South”  – lack of stable electricity at home.  There are still vast sectors within cities where reliable power is absent. Over the past week, I have had heard that staff need to send laptops back to the office to be charged so that they can continue working. This requires staff to move around and mix, which goes against our practice of trying to stop this virus from spreading.

So here are a few ideas to overcome the problem.

  1. Power consumption: Before we explore any power solutions, it’s important to have an understanding about how much power is needed to keep a staff member productive. Effectively we need to create a power budget. The idea here is to strip consumption back to the absolute minimum so we only need to build the smallest power solution and keep costs down.

    So basic needs are:
    1. Laptop computer (Without the external monitor as this uses extra power!)
    1. Mobile phone and or a 3G/4G hotspot
    1. LED light for the workplace.

Mobile phones and most 3 or 4G hotspots / dongles can be powered directly from the computer (but will reduce computer battery life). Portable solar powered lanterns can also be a great solution for the home office. If possible, try to avoid using additional technology like printers, scanners and external monitors if you can.  The camera on a mobile phone can be used as a very effective scanner with apps like Microsoft Office Lens. Online electronic signature software should also be used by organisations so that there is no need to print hard copies for signature.

Interesting Fact: During the Ebola Crisis, medical staff did everything online – including prescriptions as paper is a great medium to pass a dangerous virus between people!

The laptop is the main consumer of power so we need to understand how much power the laptop will use so that we can size up the correct power solution. Our target should be to provide enough power so that the computer will run for at least 8 hours. Ideally I would like to cap it at 8 hours in the interest of work-life balance, but some people may need to work for longer periods, especially if they are supporting the COVID-19 response.

The basic rule of physics which applies here is this:  Larger power needs require larger power systems, hence more costs!  So one quick win here is to look at the office computer estate and if possible, carry out some temporary redistribution so that the more power thirsty computers are allocated to staff that live in places where there is stable power. This will leave the more efficient computers for the people who live in the off grid areas.

So here are some power budgets for two popular computers used by NGOs

Model Lenovo X390 Lenovo T470p
Power adapter 65W 90W
Battery Capacity 48 WH 48 WH
Battery Life 3.8 hours 2.5 hours
  • Battery life is subjective to how the computer is being used.

The X series computer would be a better computer for a power starved setting it needs less energy (65W) to charge, and the battery last longer.

TIP: Computer battery life can be extended by using power save function on the laptop, and by installing larger battery packs (But larger batteries take longer to charge!)

  • Unreliable power scenario: In this scenario, we will look at what solution we could use to keep a laptop running in a location where power supplies are intermittent. The following solution is fairly cost effective.

This system is designed to use the grid power when its available  to charge up  battery. The charger should be high power, at least 30 Amps or more charging capacity. The cheaper low power charges would take too long to fully charge! The battery should be around 120 AH or more so that it can run an inverter for up to 10 hours. A 100W inverter should be sufficient to charge a laptop. Many inverters have a USB charging point built in which can power a phone.

Safety first: When a battery is charging, it can produce hydrogen gas which is explosive. So lead acid batteries should be placed in well-ventilated and away from any naked fames (such as a cooker).  

As this system supplies 220V AC, be careful that others in the house do not plug things into the system and steal your electricity!

  • No Power: For locations which is completely off grid, here is a design which should be sufficient to keep the technology running for a homeworker.

The 120W panel at peak will produce 120W energy, but it could be less when the sun is weaker earlier or later in the day. So the idea is to locate the panel in a place where it will get the maximum sunlight. The controller uses the power from the panel to charge the battery. The 20A specification means that the system can be scaled up to two panels if more capacity is needed.  

During the day, the system should produce  600-800 w/h of energy which is more than sufficient to run a computer, LED light and a charge a mobile phone.

Safety first: When a battery is charging, it can produce hydrogen gas which is explosive. So lead acid batteries should be placed in well-ventilated and away from any naked fames (such as a cooker).  

On cloudy days, solar panels will still produce some electricity but not as much as on a sunny day. As a temporary solution, this design with connecting cables should cost no more than $650. For longer term use, I would recommend doubling up on the panel and battery as it will store more power and will keep a laptop working for more than a couple of days during bad weather.

TIP: The inverter I have specified can be plugged into a car, so this is a good back up plan should energy stored in the two systems above run out of energy. Make sure that the engine is running (out in the open!) when an inverter is in use.

Conclusion: These two solutions are a “Quick and Dirty” design. It utilises components which are readily available from online retailers or hardware stores. Components can be sourced easily in global south countries. The design can also be fine-tuned to match specific power requirements by people who have experience in this field.

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