Solar For Aircon

[Naam]

The problem with aircon from solar is the high KW alternating current and Amperage needed to drive the compressor.

Whats the typical domestic ac unit running on - I guess around 3Kw - 5Kw ?

a modern 13,000 btu unit uses 1.1 kWh.

[soundman]

Another consideration is what is called a "hybrid" system which uses both solar and wind energy. Wind turbines are relatively in-expensive compared to the current P N type silcon PV cells.

I have designed a 2kw (12 knot wind pressure) wind turbine that will cost around 50,000B. (all planned - not made yet ) Equivalent in PV cells is about 250,000B.

Obviously wind is unpredictable to say the least.

(Note: emerging technology die sensitive TiO2 solar cells that can be printed on to a film of plastic on your home bubblejet printer at a tenth of the price of current technology with up to 60% of the same output will be on the market in the next couple of years.)

Both power generation sources feed the same energy storage system & use the the same inverter to supply power needs.

To run aircon and a small household - you will need a 5kw system (most likely grid connected - energy storage is not critical for a system like this.) This will require a minimum of 20 large batteries & most likely closer to 40 large batteries if you intend to use aircon overnight.

Cheers,

Soundman.

[soundman]

The problem with aircon from solar is the high KW alternating current and Amperage needed to drive the compressor.

Whats the typical domestic ac unit running on - I guess around 3Kw - 5Kw ?

a modern 13,000 btu unit uses 1.1 kWh.

Hey Naam,

Is there a formula for converting BTU to KWh consumption assuming average effeciencies or whatever?

Cheers,

Soundman.

[Smithson]

Another consideration is what is called a "hybrid" system which uses both solar and wind energy. Wind turbines are relatively in-expensive compared to the current P N type silcon PV cells.

I have designed a 2kw (12 knot wind pressure) wind turbine that will cost around 50,000B. (all planned - not made yet ) Equivalent in PV cells is about 250,000B.

Obviously wind is unpredictable to say the least.

Plenty of sun in Thailand, but little wind. Although could be viable in many other parts of the world. I would have thought a wind generator would be fairly simple, as the fans would turn the turbine. What about wind energy to power pumps? Ppl have talked about solar generators for pumps, but they are too costly.

I was told last night that electricity would rise by B3.5 a unit. Has anyone else heard this?

[soundman]

Another consideration is what is called a "hybrid" system which uses both solar and wind energy. Wind turbines are relatively in-expensive compared to the current P N type silcon PV cells.

I have designed a 2kw (12 knot wind pressure) wind turbine that will cost around 50,000B. (all planned - not made yet ) Equivalent in PV cells is about 250,000B.

Obviously wind is unpredictable to say the least.

Plenty of sun in Thailand, but little wind. Although could be viable in many other parts of the world. I would have thought a wind generator would be fairly simple, as the fans would turn the turbine. What about wind energy to power pumps? Ppl have talked about solar generators for pumps, but they are too costly.

I was told last night that electricity would rise by B3.5 a unit. Has anyone else heard this?

Don't know about a price rise.

However,

I used to think that there was insuffecient wind to drive turbines in Thailand, until making some local observations.

Where I live, there is plenty of wind during the months of the SW monsoon to run a turbine at least 60 - 75% of the time.

During the months of the thai "winter" wind in my area is suffecient to power the turbine over 80% of the time.

During the other periods of the year, wind is a day by day proposition - my estimate is good for the turbine around 25 - 40% of the time.

There are obviously many factors to consider, such as turbine type, blade design, size etc. Designing blade chord lengths and angles of attack (or even variable pitch blades) to suit local conditions is quite difficult without good computer software, however, not impossible. This means that blades can be designed to suit low, medium or high velocity air flows.

Wind energy to power pumps has been around for millenia. However, through obvious advances in the last century in aerofoil design, it has become a lot easier to design a blade that is approaching the maximum efficiency in removing the kinetic energy from a moving air mass.

All just research stuff at the moment, however, I am going to give the wind turbine (and hybrid system) a go in the near future, and then I'll be able to judge what real potential it has.

Cheers,

Soundman.

[sibeymai]

Is the TiO2 material Soundman refers to the same as the thin-film technology which Toshiba is joint venturing to produce in the next year or two. It is reported that thin-film solar cells use only 1% of the silicon of conventional PV cells, but I don't know to what extent the cost of silicon affects the overall price of a solar cell.

[soundman]

Is the TiO2 material Soundman refers to the same as the thin-film technology which Toshiba is joint venturing to produce in the next year or two. It is reported that thin-film solar cells use only 1% of the silicon of conventional PV cells, but I don't know to what extent the cost of silicon affects the overall price of a solar cell.

Don't know about the Toshiba joint venture, but "pure" silicon as used in the current lot of PV cells is apparently worth $250 USD a kilogram.

The cells I was refering to are a thin sheet of plastic or glass with a thin film of tin (oxide?), covered with a film of titanium dioxide, covered with a photosensitive organic dye. The concept is based on photosythesis occuring naturally in plants.

The idea behind the thin plastic film is that a buildings windows can be covered in this & while remaining transparent, cut down heat, glare & produce electricity at the same time.

Cheers,

Soundman.

[Smithson]

Don't know about a price rise.

However,

I used to think that there was insuffecient wind to drive turbines in Thailand, until making some local observations.

Where I live, there is plenty of wind during the months of the SW monsoon to run a turbine at least 60 - 75% of the time.

During the months of the thai "winter" wind in my area is suffecient to power the turbine over 80% of the time.

During the other periods of the year, wind is a day by day proposition - my estimate is good for the turbine around 25 - 40% of the time.

There are obviously many factors to consider, such as turbine type, blade design, size etc. Designing blade chord lengths and angles of attack (or even variable pitch blades) to suit local conditions is quite difficult without good computer software, however, not impossible. This means that blades can be designed to suit low, medium or high velocity air flows.

Wind energy to power pumps has been around for millenia. However, through obvious advances in the last century in aerofoil design, it has become a lot easier to design a blade that is approaching the maximum efficiency in removing the kinetic energy from a moving air mass.

All just research stuff at the moment, however, I am going to give the wind turbine (and hybrid system) a go in the near future, and then I'll be able to judge what real potential it has.

Cheers,

Soundman.

Let's hope I'm wrong about the price rise.

You live in Prachinburi, is that right? We're thinking about moving to a neighboring province. Is the wind in that area stronger than Bangkok?

I encourage you to keep trying, there's lots of cold overcast countries with plenty of wind. I've also read about wind power kites that sit at a much higher altitude where the wind is stronger. Have you seen the kites they're attaching to ships?

[Naam]

The problem with aircon from solar is the high KW alternating current and Amperage needed to drive the compressor.

Whats the typical domestic ac unit running on - I guess around 3Kw - 5Kw ?

a modern 13,000 btu unit uses 1.1 kWh.

Hey Naam,

Is there a formula for converting BTU to KWh consumption assuming average effeciencies or whatever?

Cheers,

Soundman.

there's no formula Soundman as technology steadily advances. 30 years ago a 13,000 btu/unit would have consumed more than double the energy of today. better designed heat exchangers and evaporators and the materials for the afore-mentioned used are playing a big role. the change from piston to rotary compressors, etc. that all added up to the present power savings.

notwithstanding these facts a lot of cheating is going on. e.g. you don't find a specsheet in Asia which specifies UNDER WHAT PREVAILING CIRCUMSTANCES (outside temperature, outside relative humidity, inside temperature, inside relative humidity, voltage) the unit's cooling capacity is x-thousand btu. you are getting nothing but bla-bla. on top of that aircons lost (depending on room heights and mounting heights) actually up to 20% efficiency as for cost saving reasons air inlet and outlet were reversed. the reason for this is to use one technical design for heatpumps and cooling only units. in my view an absolute nonsense when applied to South-East Asia!

rule of thumb for the last 4-5 years is (btu x 0.085) = kWh. for smaller units like 9,000 btu the factor is 0.9, for bigger units (18-36k btu) the factor is 0.8.

[Maizefarmer]

The problem with aircon from solar is the high KW alternating current and Amperage needed to drive the compressor.

Whats the typical domestic ac unit running on - I guess around 3Kw - 5Kw ?

a modern 13,000 btu unit uses 1.1 kWh.

Sorry Naam - with respect I must disagree:

1.0 kilowatt (kW) = 3400 Btu/hr (plus/minus a few btu - depending whose figures one wishes to accept but 3400btu p/Kw is about right).

In typical Thai temp/humdity conditions you require +/- 5,1 -5,8btu p/cubic foot of still air (meaning a room with no open windows or doors to the outside enviroment) to drop the temp from around 30C - 32C to a comfortable +/-24Celcuis, and then around 4btu p/hour to sustain around 24C

The only way I can see 13 000btu equivilant for 1.1kw is in an enviroment that is a very small volume/room, with an ideal temp differance to start with, for example the sort of conditions one could find in a northern European climate, where the temp differential the aircon would have to sustain would be very little to start with - in which case, yes, I can just possibly see a manufacturer being able to demonstrate a set of theoretical figures, or figures that are in-line with a set of aircon enviromental conditions that in reality would be difficult to repoduce in real world conditions, but next to impossible in Thailands enviroment/climate.

Edited February 21, 2008 by Maizefarmer

[Maizefarmer]

I should also add that a lot of abuse takes place in the marketing side of air-cons (er ...excuse pun) - deliberate by dealers and manufcaturers.

BTU and Kw are different units - Btu is a measure of energy wheras Kw is a measure of power, and what is significant is that it is a measure of power in relation to time i.e. the amount of work down for a given unit of time. The exploitation made by air-con dealers and manufacturers is that they will quote Btu again Kw - but they convienantly leave out the time unit for the Btu.

To relate the 2 together correctly one has to include unit of time for the Btu figure, which is often left out ..... and so I can go on and on, and things become complicated and beyond being practical, or of interest of members - suffice to say that one should take a very very close look at the Btu figures given per Kilowatt for air-cons - in reality you will find the typical aircon unit will consume far more electricty than one expected it to, or was told it would - if not only because the conditions for which the figures are given are controlled theoretical conditions, but also salesman himself doesn't understand how to correctly interperate what it "says on the tin".

Edited February 21, 2008 by Maizefarmer

[Naam]

The problem with aircon from solar is the high KW alternating current and Amperage needed to drive the compressor.

Whats the typical domestic ac unit running on - I guess around 3Kw - 5Kw ?

a modern 13,000 btu unit uses 1.1 kWh.

Sorry Naam - with respect I must disagree:

1.0 kilowatt (kW) = 3400 Btu/hr (plus/minus a few btu - depending whose figures one wishes to accept but 3400btu p/Kw is about right).

no disagreement Maizefarmer as you and me are talking about different things.

you: energy conversion kW/h / btu/h

me: energy consumption / cooling capacity

people quite often confuse both or get confused. only yesterday a friend of mine grinned and said "perpetuum mobile?" when he saw the work going on in my pool area and i explained that my 36,000 btu/h aircon unit which uses 3.05 kW/h will heat up my pool water with a heating capacity of 11.0 kWh and that this energy is free of charge as i am paying already for the cooling.

[Naam]

I should also add that a lot of abuse takes place in the marketing side of air-cons (er ...excuse pun) - deliberate by dealers and manufcaturers.

BTU and Kw are different units - Btu is a measure of energy wheras Kw is a measure of power, and what is significant is that it is a measure of power in relation to time i.e. the amount of work down for a given unit of time. The exploitation made by air-con dealers and manufacturers is that they will quote Btu again Kw - but they convienantly leave out the time unit for the Btu.

that's what we were taught when we were young boys Maizefarmer but today this statement is incorrect since years kilowatt is also used for cooling capacity and various other energy measures. there again -confusing for the layman- is e.g. input 1kWh power consumption = cooling capacity 3.8 kW = perpetuum mobile.