Driving a car on Eigg – A 10 day sample

Bruce-the-buggy under development at Edinburgh College

Bruce-the-buggy under development at Edinburgh College

We plan to run a trial of an electric buggy (Bruce) on the isle of Eigg in partnership with  Edinburgh College and Eigg Box.

The aim is to test the feasibility and value of an ultra lightweight electric vehicle on a small island like Eigg where the electricity is generated from renewable sources, all the journeys are short and diesel has to be imported by ferry from the mainland. This is very different from the requirements for electric vehicles on the mainland.

In September 2013, we visited Eigg in our Twizy which worked really well on Eigg’s “main” road but struggled with the rough tracks leading to people’s houses. The Twizy also has little load carrying capacity which is vital on the island where all supplies have to be collected from the ferry. This is why we are trialling an electric buggy.

Prior to the buggy trial, we are trying to gather some data on typical vehicle trip lengths, speed and frequency. The island is about 2 miles wide by about 5 miles long.

Bruce-the-buggy has a top speed of 50mph but travels more comfortably at 20 -30mph. His range is likely to be around 15-20 miles (depending on speed, hills and load carrying).

So, how well might this fit an Eigg resident’s travel patterns?

We equipped one helpful Eigg volunteer with a simple vehicle tracker for a 10 day period in March. The tracker isn’t 100% reliable but hopefully captured most of the movements of this one household’s vehicle for that period.

We recorded 24 trips in the 10 days and a total mileage of 81 miles. Below you can see the track of the longest continuous trip recorded (8.34 miles) from home in Cleadale via a neighbour’s property to the Ferry pier at Galmisdale and back home via a property at the Northern end of the island.

Car trip Cleadale to Ferry

Car trip Cleadale to Ferry

The chart below shows the frequency of car trips of different lengths.

Length of Car Trips (miles)

Length of Car Trips (miles)

The trips were all less than 10 miles long and 42% were less than 2 miles. Daily mileage was less than 10 miles on 8 of the days and the maximum on any day was 17 miles (3 trips). Given Bruce’s likely range of 20 miles, this suggests that he will happily cover all of a day’s journeys even if only re-charged once at night. If so, he will hopefully be consuming electricity when it is most readily available on the island.

The next table estimates the electricity consumption and cost per day if these trips were done in Bruce-the buggy. We don’t yet know but think Bruce may average 4 miles per kWh and we are assuming the cost of electricity on Eigg is 22p/kWh.

Electricity consumption & cost

Electricity consumption & cost

On these estimates, the average cost of these trips made in Bruce would be 45p/day. If we assume a typical Eigg vehicle averages 8 miles per litre and a diesel price of, say, £1.36 then the equivalent cost would be 3 times greater (£1.36 per day).

Bruce is much slower than an ordinary car but we hope that will be less significant on Eigg. The next chart shows how fast the Eigg vehicle was travelling for what percentage of time. This is based on over 3000 samples taken every 5 seconds by the tracker.

tripspeed

Sampled speed of car

Reassuringly, this Eigg vehicle only made it to 50mph once in 10 days. 98% of the time it was travelling at 30mph or less and 68% of the time it was travelling at 20mph or less. This suggests that Eigg drivers won’t even notice that Bruce has a lower top speed than their cars and trips to the opposite end of the island will not take any longer.

We hope to collect further data on the car trips which different Eigg residents take but assume this is a fairly typical pattern given the limited size of the island. Bruce-the-buggy will have more sophisticated logging built in and so we will have accurate data on all the trips he makes – distance, speed and energy consumption.

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About Alison Kidd

Research Psychologist
This entry was posted in EV Research and tagged , , , , , . Bookmark the permalink.

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