Sunboats: Solar-electric Powered Water Transport

by G Simcock and P McLaughlin, Prince Alfred College, South Australia

Introduction

Staff and students of Prince Alfred College, a Uniting Church school for boys in Adelaide, South Australia, have built two solar-electric powered vessels suitable for travelling on inland waterways.
 The idea for solar-electric boats developed from interest in the World Solar Car Challenge, a 3,000 km race across Australia from Darwin to Adelaide. The staff and students of the College set themselves the challenge of traversing the entire navigable length of the River Murray, some 2,000 km in all.

Design and Construction

Four staff and up to 100 students participated in designing and constructing the craft and in the two expeditions along the River Murray.

Sunboat

The first boat to be constructed, Sunboat, was a catamaran with two round-bottomed hulls separated by a pod for the crew. The hulls were constructed of closed-cell polyurethane foam, coated on both sides with fibreglass. An awning over the pod gave the crew some protection from the sun.
 Power was provided by Siemens Showa 53 W solar panels, connected in groups of eight to make up banks of panels. Four of these banks were used, two in front of the pod and two behind, giving a total of 1,152 cells. Two Evinrude 12/24 V underwater electric outboard motors were mounted at the back of the pod. In each hull were two 12 V deep-cycle batteries connected in series, with forward panels connected to one set and aft panels connected to the other.
 Overall, the boat was 10 m long and 4 m wide. Steering was by way of rudders fitted to the stern of each hull, operated by a pull-cord.
 Sunboat completed its 2,000 km journey down the River Murray in 28 days, creating three records. The average distance covered each day was 71 km and the boat's top speed was 10 km/hr (with the current).

Sunboat II

The second craft, Sunboat II, built on the experience gained with Sunboat, provided full accommodation for six people.
 Many designs were created and explored before the final design was chosen. The main hull is 11.28 m long, 2.35 m wide and 2.4 m high. Smaller hulls, 9.3 m long, are hinged each side of the main hull to give an overall width of 5.49 m. Folded down and locked into place, these provide stability, while allowing the craft to be transported by road when folded up.
 The same solar panels were re-configured into groups of four and additional panels added to give a total of 1,728 cells in 12 groups. Six groups are hinged from each side of the roof of the main hull and are wired to charge and run a 36 V system. Twelve deep-cycle 6 V batteries, connected in series of six then parallel, are stored beneath the floor. Four smaller solar panels are mounted along the roof to charge two 12 V batteries supplying electricity for the internal lighting, refrigerator, two-way radio and satellite phone.
 A 36 V DC series-wound motor, mounted in a tilting bucket above the foot of an outboard, provides propulsion. A variable speed controller varies the current used and hence power produced by the motor.
 Sunboat II left Yarrawonga on 1 December 1995. The river level was low, exposing many snags, but the boat's shallow draught (35 cm) enabled it to proceed with caution. In good conditions the boat reached a speed of 13 km/hr. Daily distance covered was between 60 and 85 km.
 On straight sections of river in early morning or late afternoon the panels on one side could be dropped to a 45 degree angle to continue charging the batteries while maintaining travelling speed.
 Sunboat II covered a total of 2,500 km in 39 days to claim a new record.

Conclusion

Sunboat II is a practical craft which has performed exceptionally well as a river boat. It is well suited for travel on sensitive waterways as it creates virtually no noise, no smell and no oily deposits, and the wake does not erode the river banks.
 Staff and students of Prince Alfred College have gained a great sense of achievement and many skills in designing and operating the two Sunboats. They have developed a craft which is practical and performs well in the conditions for which it was designed.

For more information contact the CADDET Australian National Team in Canberra.

 

Note: Prince Alfred College wishes to acknowledge the help of its many sponsors, including Ford (for Sunboat) and Westpac (for Sunboat II).

The CADDET Renewable Energy Newsletter is a quarterly magazine published by the CADDET Centre for Renewable Energy at ETSU, UK.

The articles published in the Newsletter reflect the opinions of the authors. They do not necessarily reflect the official view of CADDET.

Enquiries concerning the Newsletter should be addressed to
Pauline Toole, Editor, CADDET Centre for Renewable Energy, ETSU, Harwell, Oxfordshire OX11 0RA, United Kingdom. Tel: +44 1235 432968, Fax: +44 1235 433595.