Best of inventions

You could say that Paul Kennett takes a number 8 wire approach to sustainability. 

In the last 15 years the Lower Hutt man has built his own powerwall, insulated the walls of his home using a hairdryer and polystyrene beads, made spare parts for electric cars using a 3D printer and is now working on building a second battery for his Nissan Leaf. 

He’s fairly understated about it: “I just tinker away on finding cheap solutions for problems that I have around the house.”

Around 2004, Paul started reading up about – and then freaking out about – peak oil and climate change. A solutions-focused kind of guy, that led him to Transition Towns, a community-based movement which supports people to become self-sufficient and prepare for life after oil.  

“The Transition Town movement seemed to me to be a rational, sensible approach to transitioning to where we needed to be.

“We don’t have a huge amount of money but I do have a bit of ingenuity. So I needed to find cheap solutions.” 

Paul Kennett in this workshop
Paul Kennett “tinkers” to find solutions to problems he has at home.

One of his first DIY projects was insulation for their home in Moera, an old workingman’s cottage. 

After insulating the floor and the ceiling with Batts himself, he recieved a quote for $5000 for the walls. Paul thought he could probably do better. 

“I realised you could drill holes in the walls to blow stuff in, I found a cheap source of recycled polystyrene and then I spent a lot of time figuring out clever ways of blowing it in.” 

He tried hairdryers first, which he found quickly clogged up with dust, then a vacuum cleaner that had a blow function, and then upgraded to an air compressor. 

It was slow, tedious work, says Paul, but after eight months their walls were fully insulated for next to nothing. 

A researcher came to test the heat retention and energy efficiency of the wall insulation a few years after Paul had finished the job, and confirmed that the polystyrene beads hadn’t settled. That means they’re unlikely to ever need a top-up, like other insulation does. 


Paul and his family are proud to say they live in a fossil-fuel free home. 

Part of what makes that possible is their 1.5kW solar panel array and the powerwall that Paul has made from recycled laptop batteries. 

It’s perhaps not the kind of thing just anyone can jimmy together. 

Paul started an electrical engineering degree when he was younger, before being pulled into IT. 

He’s always been big into biking (he’s one of the-famous-among-cyclists Kennett Brothers) and eventually got into repairing electric bikes, which taught him  about the lithium batteries inside electric bikes.  

From there he started to see their potential. 

New Zealanders produce an estimated 89 million kilos of e-waste each year, a good chunk of it batteries. A small amount of those batteries are sent by conscientious consumers to recyclers – so that’s where Paul went for his next project. 

After sifting through some unsorted batteries at a recycling business down the road, he walked away with between 400 and 500 laptop batteries. On testing them at his workshop at home, he found about 70 percent of them were still good for re-use. 

Paul explains that people often get rid of their laptops because of an issue unrelated to the battery – a cracked screen for example – or without realising that it’s in fact only one of the five or so battery cells inside the laptop that have died. 

He created a casing that the battery cells could sit in (using his 3D printer), rigged them all together, and wallah – a powerwall that rivals the $15,000 Tesla powerwall. 

It allows the family to store the energy generated by their solar panels, and Paul has it wired so his garage workshop and the lights in the house run off it. It’s the equivalent of about $100 worth of power a month.

And will the batteries eventually run out? 

“[The batteries] have a finite life, I just haven’t discovered what that is yet. It’s been running now for five years, from used batteries.” 

Homemade powerwall by Paul Kennett
A section of the powerwall Paul made and uses to run the lights in the family home.

Paul’s energy is currently being put into tinkering with the family’s Nissan Leaf. 

The batteries in electric cars degrade by about three percent a year, due to age and use. So Paul’s now working out how to build a second battery – again using recycled battery cells – to extend the car’s range as it ages.

He’s also making use of the 3D printer they have at home to make spare parts for the car, focused on making the car more aerodynamic and therefore more energy efficient. 

There’s a roaring secondhand market for electric car parts in New Zealand. As the cars are all imported, and specialist electric mechanics are few and far between here, electric car owners are often fixing stuff themselves. 

A crashed Nissan Leaf, which can be stripped for parts, will have plenty of takers on Trade Me. 

Converting New Zealand’s motor vehicle fleet to electric could make a huge difference to our country’s carbon footprint – with 84 percent of our electricity generated from renewable sources, it’s an easy way to reduce our emissions, says Paul. 

Before the Leaf, the Kennett family were car free for 14 years. 

It came about after Paul started measuring and putting numbers on the family’s carbon footprint. 

“Once you start measuring your carbon footprint yourself, it becomes pretty clear how much you need to do and what needs to be done. 

“Getting rid of the car seemed a reasonable step. In order to make it less daunting, we said, okay, we’re only going to do a six months’ experiment — that lasted 14 years.” 

Paul says that strategy – calling a small change a short-term experiment, taking baby steps – has been a successful way of bedding in long-term change. You just get used to it, and you start planning around it. 

It got them started on cutting meat out of their diet, and not flying anywhere. Paul now hasn’t flown anywhere since 2005. It’s been tough at times — for example, missing family celebrations — but having kept it up for 15 years he’s now more determined to keep going. 

Paul Kennett in workshop with the Kennett powerwall
Paul in his Moera workshop, the Kennett powerwall behind him.

Asked why all of this is worth the effort, Paul is very clear on his motivation. 

“My rationalisation is action on climate change needs to occur at every scale. Globally, nationally, locally and individually. 

“Of those different scales, I have the most control over what I do individually. To me there’s no way around it. I need to manage my actions and behaviours, and do what I can at the other scales. 

“In order for us to preserve some sort of mental health, I need to not also blame myself for the complete failure at those larger scales. We are up against the world’s richest industry.” 

“It gives me something to do, something I can do. I can change me, I can’t change Donald Trump.” 

To find out more Paul’s insulation project, check out this detailed rundown on how he did it.

For more on his family’s choice cycling guides, go to the Kennett Brothers’ website.

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