In the last edition, I highlighted the challenges faced by home workers who live in locations where the power supply is either intermittent or is not available at all. Since the article was published, I have carried out rigorous testing of two systems. Both performed well. One system was “Out of the box” and the other system was built from separate components I was able to source from suppliers in the UK.

The quickest solution is to buy a solution which has been pre-built. But with the world in lockdown and many flights cancelled it may not be possible to import solutions, so the “Build your own” option may be the only way to provide power. In addition to the home solar designs below, I was recently asked to look at design for 20 staff.

Voltaic Arc 20W Solar Charger Kit: This system is supplied by Planson International. Over the course of four days, I was able to use a Lenovo X390 laptop without needing to connect to the mains power to top up.

The Lenovo X90 uses around 65 Watts when charging which is a little more than the capacity provided from the solar panel, however it only takes just over an hour to charge. Testing was conducted in the UK during sunny weather (early April). During the testing enough energy was created to produce two full laptop charges a day.

It is also possible to get more from a charge by doing the following:

• Use battery save functions
• Do not play music – it consumes power
• Reduce the screen light power (try to work in a shaded place
• During conference calling, avoid video if possible.

The Voltaic kit also comes with a LED light which is more than sufficient for a desk and a mains charger which can be used to charge the battery in the places where intermittent power is needed.

 100W Home kit (Built from separate components: This system can be built from components purchased locally. In the UK, the following components were purchased from RS components (rswww.com).

• 100W Solar Panel             $160                                                 
• 100 A/H Lead acid battery                     $280
• 100W Inverter                                        $70                                          
• Controller (10A)                                          $80
• Cables and plugs                                        $80

For a total of approximately $680, this system is sufficient to power a few LED lights, a laptop, mobile phone and a printer. The purpose of the controller is to manage the power from the solar panel so that the batteries is now overcharged. The controller also has a display which indicates how much charge is being generated, and how much energy is stored in the battery.

This system can also be scaled up. With the same controller, two further 100W panels can be added (Bringing the capacity to 300W or 9A). Additional batteries can also be added to the system to increase storage capacity. Important Note: Energy loads must always be connected to the output terminals on the controller and not to the battery directly. This will prevent the battery from being completely drained (which can cause damage to the battery).

The inverter in this design provides a maximum power of 100W. Larger inverters can be used, but till consume power more quickly. Given that it often takes just over an hour to charge many laptops, I think a single invertor will be sufficient for charging laptops.

For lighting, I would recommend 12V LED lights rather than using 220V lights connected to an inverter. This is more energy efficient as there are often energy losses within most inverters.

Small office Design for 20 users

When designing a system for a small office, it’s important to work out what the overall load is. This will help to identify what components will need to be purchased to build the system. Once the system has been set up, it must only be used for the power load it was designed for. If more items are loaded (e.g. more computers) the system may not have the capacity to support the increased load without upgrading the solar system first.

Many years ago, I developed a tool to estimate the size of a solar energy system. This first screenshot lists the items we need to power.

The load list does not contain items like fridges and security lights as I would recommend buying dedicated stand-alone solutions which have their own panels built-in. Please note that in addition to power load information, it’s important to include information about how long each item is used each day.

The next table calculates the amount of panels and batteries needed to provide the power for the load listed in the first table. The battery bank has been specified to store enough energy for three days. The solar panel has been designed to produce enough energy to service the load and provide a little extra power which can be used to store up energy for three days.

So for this load, if we use 100W solar panels, and 100A/H batteries, we will need 29 Panels and a bank of 50 Batteries. In addition to this, we will need a fairly large controller which can handle 150 Amps. Larger controllers also require bigger cables to transfer the power. In some places higher capacity cables and controllers can be difficult to source, but it’s possible to achieve the same result by building three smaller 50A systems.

As a very rough guide, here is an estimate for building the system above.

• 150 Amp controller:        $2300
• 50 Batteries:                      $1250
• 29 Panels                             $4640
• Inverter 2KW                     $1000
• Cables etc                            $1500
  Total                                    $10,690

This is a rough estimate which does not include shipping and taxes. Whilst the initial set up cost is high, over time, the overall return on investment is good as no fuel is used. The only component which needs to be changed from time to time is the batteries.

Conclusion: Solar energy can be a great solution for remote locations where power is not available. It is also a cleaner method of providing energy. With some good planning, selection of low powered office systems, smaller power systems can be purchased. Good discipline is also important as it’s easy for a system to fail to deliver if extra load is added which was not planned for.  

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.

Around the world, the use of wind and solar farms is increasing as the efficiency of panels and wind generators increase and production costs fall. In the global north, the large renewable energy plants feed power into national grid systems which means that we can reduce our carbon impact by using the gas, coal and oil fired power stations less. But, there is an issue. Whilst we can produce plenty of energy from energy farms, we have not yet really figured out how to store the megawatts of energy efficiently. During a cycle ride from London to Gibraltar last year, I passed through many wind farms in France and Spain. On windy days, there were times when only have of the turbines were not turning. So whilst we have all of this infrastructure, the maximum benefit cannot be realised as we do not have the technology to facilitate the mass storage of electricity.

For smaller solar systems like the ones we would use in the aid sector to power a school or a clinic, the same power storage problem exists. In most countries we store energy in lead acid batteries or some other variant. The use of Solar systems can reduce the carbon footprint, but at the same time we are producing a lot of environmental waste which is not good for the communities where the aid sector is meant to be “doing no harm”

The Battery Problem: The most widely used component in a small solar system is the lead acid battery. The same battery as we use in vehicles. In a vehicle, the lead acid battery normally lasts up to three years which is its expected life. This is because the engine will keep the battery charged. In a solar system the lead acid battery may last two years if we are lucky. Unlike in a vehicle, the battery will frequently be drained to less than 50% of its capacity. If this happens often, longer term damage occurs in the battery cells. The hot climates where NGOs operate also has a negative effect on the battery shortening its life further.

Given the short life span of lead acid batteries, the by-product of the green solar systems is a lot of toxic waste. This is can be a massive issue in developing countries where they are not geared up for recycling.

Lithium Ion batteries are often seen as a good alternative to lead acid batteries because they can hold more charge. But there are some major disadvantages. Lithium Ion batteries contain some very toxic chemicals and have a troubled history of catching on fire. Most airlines will not transport larger lithium batteries due to the fire risk.

An alternative approach:  There are better technologies and in the future we will see innovation come from the automotive industry.  Tesla and other manufactures of electric cars are working hard to develop battery technology which will allow electric vehicles to go much further than they can today. As vehicles move from petrol and diesel to electric, the mass production of new battery technologies will bring the cost of energy storage down. Where the automotive industry produces answers for energy storage, in the aid sector, we will be able to take advantage of new battery technology for our solar systems.

We have been using electric vehicles for many years and there are already battery technology we can use now to make our solar systems more sustainable. Schneider Electric uses Nickel Sodium batteries to store energy in its Vilaya range of solar systems.  

The Nickel Sodium battery (This example made by FZSoNICK) works in an interesting way. The battery need to be warmed up so that the salt inside melts. Once the battery is at its operating temperature, energy can be stored and discharged as needed. The lifetime of the battery is 13-15 years. At the end of life, the waste product is a block of salt and some associated electronics.

The FZSoNICK has the ability to store 10 KWH of energy in this single unit. The cost for one battery is roughly $10,000. It’s a big upfront costs, but there is a return on investment over time. So let’s take a closer look at the numbers.

A good quality deep cycle 90AH battery will cost around $(US)250 and can store 1KWH of energy. Taking in account that we don’t want to discharge a lead acid battery than 40%, then we need to buy more batteries than the stated capacity to ensure that we can store and use the 10KW without damaging the battery bank. So for this example, we would need to buy 14 lead acid batteries at a cost of  $3500. As the lifetime of the battery is likely to be two years or less, over the course of 12 years, we would need to change the batteries 6 times, which comes to a total of $21,000 or more. This does not include other costs such as installation and shipping.  

So whilst there is a higher start-up costs, the return on investment is significant. But there are other advantages which you will see in the following summary:

• Cheaper to run over a long period
• Batteries take up much less space which means less cables are needed for installation.
• No fire risk from gasses such as hydrogen
• End of life waste is smaller as this technology does not use as many materials as other batteries. The main waste product is a block of salt.
• Battery is stable and safe to transport
• Good return on investment

Deployment example: Nickel Sodium batteries are built into complete systems such as the Villaya solar system from Schneider Electric. The solar plant is transportable with electronics installed and fixed to the walls of the an ISO container. This approach is great for disaster preparedness due to its mobility.  

This system can produce enough power to run a small office. In addition to the power circuits, communications technology can also be fitted inside the container so that internet connectivity can be provided in addition to electricity.

The Villaya system is designed with the appropriate systems to protect the circuits from lightning, which means that this system is very well suitable for topical and sub-tropical locations such as Africa.

For disaster response, where it may be difficult to move a container quickly, it’s possible to design the same system into other  formats which can be broken down to smaller shipping units for future assembly at a disaster site.

Sustainability: We know that solar panels have a long life if looked after. Nickel Sodium Batteries also have a long life which means that a system built on this technology will be sustainable, but technology is not the only area we need to make sustainable. We need to build peoples capacity. As we adopt new sustainable technology, with built in monitoring systems, these systems will become more complex. We need to initiate a training programme to build the skills of the people who will source, install and maintain solar energy systems.  NGOs will have a massive role to play here as they work in very remote locations. If they can adopt green energy systems instead of generators, other sectors might do the same.

In my next article, I will discuss how we in the aid sector should establish teams within our organisations to take ownership of environmental affairs and build the skills in house to help reduce the carbon footprint.