Analysis of Marine Solar Power Trials on Blue Star Delos: By Greg Atkinson

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In October 2014 the high speed car and passenger ferry Blue Star Delos was fitted with a marine solar power system. This was done as part of a project to study the use of renewable energy on large ships. In May 2015 while the ship operated in the Aegean Sea, the performance of system was checked and a range of data collected.

Eco Marine Power CEO, Greg Atkinson has published a paper which is focused on the analysis of these data and the evaluation of two days of system trials.

Intorduction

Solar power is increasingly used as an alternative source of energy with land-based applications including large-scale grid connected photovoltaic (PV) power stations, home solar power systems, remote power solutions and off-grid applications. However, the use of solar power on ocean-going ships has to date been limited to just a few vessels.

In 2014 the high speed car and passenger ferry, Blue Star Delos (Table 1), became the first ship of this type to be installed with a marine solar power system. This system was installed as part of a wider project to evaluate the use of renewable energy on merchant ships. Unlike smaller vessels fitted with solar panels such as the MS Tûranor PlanetSolar, Delos is a large commercial ship.

It has the capacity to transport 2400 passengers and 430 vehicles (Blue Star Fleet) and typically departs daily from the Port of Piraeus, Greece, at 07:25 and returns at 23:25. The ship is a vital transport link to several islands in the Aegean Sea and often operates in harsh conditions with apparent wind speeds of over 50 knots having been observed. The ship also incorporates many innovative features including highly efficient shaft alternators for electrical power generation.

The trials on Blue Star Delos demonstrated that under operational conditions at sea, a low-voltage marine solar power system using thin panel PV technology and energy storage could provide a continuous stable supply of power to a DC load.

The power output of the system met or exceeded design expectations and the performance of the PV panels did not appear to be significantly impacted due to the build-up of dirt and salt. However, analysis of data over a longer period needs to be undertaken and the possibility to improve the power yield by adjusting system parameters requires investigation.

Additionally the impact of the marine environment on the solar panels and aluminium frames requires further study including determining how frequently the marine solar panel array should be washed and maintained.

Delos Ship Solar Power

The full results from these trials have been analysed by Eco Marine Power and several improvements were incorporated into its Aquarius Marine Solar Power solution. These improvements include the addition of hybrid VRLA batteries manufactured by The Furukawa Battery Company, the development of specialized mounting frames for ship mounted photovoltaic (PV) panels and additional features added to the Aquarius Management & Automation System (Aquarius MAS).

During 2019, further selected research and technical papers will be released and made available via EMP’s Research & Development webpage. More detailed analysis including ship renewable energy surveys & system designs will also be available via EMP’s design and consulting services and/or discussed with ship owners during ship renewable energy projects.

Purpose and methodology

The primary purposes of the system trials were to compare the predicted energy output with measured values, evaluate the operational performance of the PV system and confirm that continuous power could be supplied to the test load. A range of data were collected and recorded between the 17th and 20th May including information stored in the MPPT charge controllers during the previous three months. Two system evaluation trials were conducted on the 17th and 19th May as the ship sailed from Piraeus to Ios, Naxos, Paros, Santorini and on the return journey to the Port of Piraeus late in the evening.

Evaluation and trial results

On the day of first system trial on 17 May the solar panels had not been cleaned since installation in October 2014 and it was observed that they were unevenly covered in a light layer of dirt and salt. This was expected to impact the energy production of the PV system to some extent. Before the second evaluation voyage on the 19th May the panels were thoroughly cleaned and all surface dirt and salt removed. On both trial days the weather was warm and sunny with cloudless skies. Seas were calm and the apparent wind speeds were generally in the range of 20–25 knots when the ship was underway. The test load comprised of two 24 V 50 W LED floodlights and two sets of 24 V 216 W LED strip lights connected to the output of the 24 V battery pack. The total load provided by these LED lights was approximately 532 W.

During each day of the trials the energy produced by the PV system was similar and no degradation in performance due to the solar panels being unwashed on the 17th May was apparent. System power output at 30-minute intervals based on data from the two days of trials is shown in Figure 6. The average energy produced was calculated as being approximately 13,500 Wh or 13.5 kWh. This is higher than the estimate for May but taking into account the power output tolerance of the PV panels (+/– 5%) and that the trials were conducted on two cloudless days in mid-May then this is within an acceptable margin.

Conclusions

The trials on Blue Star Delos demonstrated that under operational conditions at sea, a low-voltage marine solar power system using thin panel PV technology and energy storage could provide a continuous stable supply of power to a DC load. The power output of the system met or exceeded design expectations and the performance of the PV panels did not appear to be significantly impacted due to the build-up of dirt and salt. However, analysis of data over a longer period needs to be undertaken and the possibility to improve the power yield by adjusting system parameters requires investigation. Additionally the impact of the marine environment on the solar panels and aluminium frames requires further study including determining how frequently the marine solar panel array should be washed and maintained.

Lastly, the utilisation a low-voltage PV system or systems together with low-voltage DC loads is a topic that requires further research. DC LED lights, for example, typically consume 1/5 of the power to deliver the equivalent level of illumination as higher voltage AC lights. Therefore it should be possible to significantly reduce the load on the ships’ generators by using a combination of marine solar power and LED lighting technologies.

(Author: Greg Atkinson, Founder and Chief Technology Officer at Eco Marine Power)

Sea News Feature, January 8