A ship without sea water pumps……..what!

[Shaun Wright]

As an energy consultant I am always looking to identify heat recovery /waste heat opportunities whilst on site (yes, a sad obsession). For some time now I have questioned the need for sea water pumps. Preventing the operation of a sea water pump can save between 10-40kW, depending on the size of ship, and a reduction in boiler operating times/costs whilst in port. This would result in good financial and CO2 savings.
The waste heat / water return from the main and auxiliary engine ‘jackets’ is constant (24/7) and of good quality (70-90.C) which provides an excellent opportunity to utilise this waste heat. Furthermore there are a number of opportunities/applications on board where this waste heat could be used (fuel tanks/heaters, HVAC, DHW and fridge system defrost).
Most ships have exhaust gas economisers providing ‘free’ steam and are designed to meet most of the on board heating requirements whilst at sea. The need to redesign the cooling systems to utilise the waste heat may not be consider being a priority. However there are a considerable amount of heating requirements on board and without any major cost these systems could be incorporated into the design of the engine room or even retrofitted in some cases.

In port there are numerous opportunities to utilise this waste heat, from the auxiliary generators, which should limit the operation of the main boiler and sea water pumps. A simple application would be to heat DHW, the main engine ‘jackets’ or HVAC systems.
So, do we need sea water pumps on a ship?

[Martin Borgh]

Excellent idea - I'm investing similar concepts myself but from a slightly different approach. Have you ever considered using the heat with a themo electric generator (or other heat-engine type apparatus) to make electicity?? You would in most cases where you would use a heat engine still require a sea water cooling system to make sure there is a large enough temperature difference to drive the device - but at least you would get something from the waste heat instead of just dumping it into the sea...
I'm also looking into the possibilities to drive a cooling device with the excess heat (a adsorption refrigerator in effect) which seems to be a reality today - the below is a text excerpt found on the internet:
Mr. Stig Remøy and his Norwegian company Olympic Prawn. The new ship, yet to be named, will be build at Havyard Solstrand in Norway, and the ST-118 design is worked out by Skipsteknisk in Ålesund. http://www.skipsteknisk.no/default.asp?menu=32&product=50


The sum of the contract value will be in the area of € 2 million. This includes the absorption system, compressor for redundancy, control system and installation work. GEA Grenco B.V. leverantör av adsorptionsteknik.
Fuel saving:
While traditional refrigeration systems are powered by electric energy, the absorption system is powered by surplus heat from a diesel engine. Knowing that electrical energy onboard a ship is generated through burning of increasingly more expensive fuel, use of surplus heat provides substantial savings. In daily operation this new vessel will save approximately 80% electrical energy, compared to traditional use of compressor for the refrigeration. On an annual basis this adds up to a saving of more than two hundred thousand litres of fuel.

Any thoughts on such concepts??

[Kristinn A. Aspelund]

Absorption refrigeration is quite interesting concept. We at Marorka have done some studies and consulting work on thermodynamics involved both in heat pumps and heat recovery on ships. And this is quite interesting field with big potential. I've done some work on that in the past most though on research level. This is not a new subject in that sense, for example Dr Sam Shelton my tutor in GATech has been studying the Einstein cycle , which is a refrigeration cycle patented by Einstein in 1930. One of the interesting factors of the Einstein cycle is that it has no moving parts, it uses boiling as pump similar to coffee percolators.



I think the Olympic Prawn project is quite interesting. Do you know if it is still on after the bankruptcy of the Solstrand Yard?

Kristinn




Martin Borgh said:

Excellent idea - I'm investing similar concepts myself but from a slightly different approach. Have you ever considered using the heat with a themo electric generator (or other heat-engine type apparatus) to make electicity?? You would in most cases where you would use a heat engine still require a sea water cooling system to make sure there is a large enough temperature difference to drive the device - but at least you would get something from the waste heat instead of just dumping it into the sea...
I'm also looking into the possibilities to drive a cooling device with the excess heat (a adsorption refrigerator in effect) which seems to be a reality today - the below is a text excerpt found on the internet:
Mr. Stig Remøy and his Norwegian company Olympic Prawn. The new ship, yet to be named, will be build at Havyard Solstrand in Norway, and the ST-118 design is worked out by Skipsteknisk in Ålesund. http://www.skipsteknisk.no/default.asp?menu=32&product=50


The sum of the contract value will be in the area of € 2 million. This includes the absorption system, compressor for redundancy, control system and installation work. GEA Grenco B.V. leverantör av adsorptionsteknik.
Fuel saving:
While traditional refrigeration systems are powered by electric energy, the absorption system is powered by surplus heat from a diesel engine. Knowing that electrical energy onboard a ship is generated through burning of increasingly more expensive fuel, use of surplus heat provides substantial savings. In daily operation this new vessel will save approximately 80% electrical energy, compared to traditional use of compressor for the refrigeration. On an annual basis this adds up to a saving of more than two hundred thousand litres of fuel.

Any thoughts on such concepts??

[Tatta Seshu Raghavacharyulu]

Dear Mr.Wright,

Greetings

You are right. As other said correctly the waste can be used for HVAC of accommodation, even engine room too. Though the initial cost of waste heat operated absorption chiller systems(li+br & Ammonia, water) for refrigeration and air conditioning. Cargo cooling of containers also can be made possible with this waste heat.

Advantages- CFC minimize, power reduce, Increase life of machinery, minimize the machinery, effective utilization of waste heat and bring down global warming, many more...

I will be happy to contribute for this mission.
kind regards
TSR CHARY

[Rubina Bahar]

this has been a good idea. I am trying to focus on using all possible waste heat source in a ship and provide desalinated water. I do not have much info about a ship's different working systems; what type of engine is used and what kind of heat exchangers are used in the 1. Engine cooling system, 2. HVAC system.
Did some search on engine cooling water but what I found was, the engine cooling water ( which is a closed circuit flow system) will not be directly avilable for use, we need to extract the heat energy from engine cooling water via a heat exchanger(Thermex 2000 series, what I could find for marine heat exchange solution), but the heat exchanger exit temperature comes down at around 40 deg Caccording to my calculation form the available data, I need atleast 65+ deg C for desalination purpose.
I would be grateful if someone can provide me with the info on engine cooling system and at what temperature the coolant seawater is thrown away in the sea.

[Kristinn A. Aspelund]

Hi Rubina,
Since ships are of different sizes and surf different needs there is no general rule in engine types. You could generalize by saying that larger ocean going vessels are operating with slow speed two stroke diesel engines (around 100 rpm)
What I’ve seen on ships then desalination plants are normally operated with heat from engines high temperature cooling cycle. In typical that is a heat source where the water temperature exiting the engine is above 90 °C. This is a better location for whr system than on the seawater cooling line since the SW is normally discharged at temp below 40°C. The amount of heat available in the HT line is normally significant, you can revert to some documentation from engine makers for the heat balance of ship engines such as MAN B&W
Hope this is of some help
Best regards,
Kristinn


Rubina Bahar said:

this has been a good idea. I am trying to focus on using all possible waste heat source in a ship and provide desalinated water. I do not have much info about a ship's different working systems; what type of engine is used and what kind of heat exchangers are used in the 1. Engine cooling system, 2. HVAC system.
Did some search on engine cooling water but what I found was, the engine cooling water ( which is a closed circuit flow system) will not be directly avilable for use, we need to extract the heat energy from engine cooling water via a heat exchanger(Thermex 2000 series, what I could find for marine heat exchange solution), but the heat exchanger exit temperature comes down at around 40 deg Caccording to my calculation form the available data, I need atleast 65+ deg C for desalination purpose.
I would be grateful if someone can provide me with the info on engine cooling system and at what temperature the coolant seawater is thrown away in the sea.

[Rubina Bahar]

Thank you very much Mr. Kristinn. So far I know there are two cooling cycle in the engine, and the high temperature cooling cycle is enclosed with special chemicals(?? ) to provide corrosion free environment for the engine body. The sea water works on the low temp cooling cycle only. Is it true?
And one more thing I wanted to ask is, why the sw is rejected to the sea at 40oC ? Is it due to the environmental constraints? or is it for better heat rejection by the engine? Can I manipulate the heat exchanger ( low cycle) coolant flow rate , thus lowering mass flow will give me higher temperature at the exit of the low temp cooling cycle?

Thank you very much for your reply

[Tatta Seshu Raghavacharyulu]

Dear Martin

Greetings

this wondeful concept of WASTE heat utilization at higher and even lower temperatures is not inspiring the ship owners due to high cost of installations.

I wish the complete engine room can be air conditioned with the main engine and DG waste heat for the vessels plying in tropical waters.

this forum is also not many people taking part and even i pushed in marine talk also. May be every ship owner is looking for a showflat and if successful then they will jump into it.

Adsorption chiller which is more favourable to operate at low temps from 60*C and at 85*c the peak performance.

i really enjoy this concept and reading once while to see that any interests in this subject.

regards
chary