District Heating System

November 9, 2008

District Heating System’s links the heating systems of a number of dwellings, buildings or units on a site or development. These links allow the system to transfer heating from one site to another increasing efficiency. This is achieved by using larger more efficient equipment located in the basement, by matching thermal demand on different sites to maximise efficient plant operation, and by using Renewable, Sustainable or Alternative Heating. It also creates cost efficiencies through improved management, reduced maintenance and the bulk purchase of fuel.

district-heating 

So does it work. Well like all large systems it comes down to the management. A well managed district heating system is far more efficient than individual well maintained boilers. In some cases I’ve come across systems that are horribly badly designed and managed. These ones suck and give the rest a bad name.

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Curtains – the best value for money energy saver

October 28, 2008

Curtains can reduce heat loss in the winter by 10% – 25% and reduce drafts significantly. So considering their relatively low cost, and other benefits, are a very good investment. They do this by providing a barrier between the window, and the main room. In general windows have the poorest U-Values in an average room, and so are the focus of most heat loss during colder times. Warm air circulates around the space due to convection and is suddenly cooled when it touches the relatively cold windows. Curtains act as a barrier to this air flow, and so reduce the amount of air being cooled.

Here are some tips to help you save energy with your curtains:

  • Actually use the your curtains when you have them available
  • The more completely the curtains cover the window the better, so have large ones with plenty of overlap and overhang at the ends
  • Lining in curtains reduce air infiltration through them, and so is well worth the investment
  • Curtains should be hung as close to the window as possible to reduce air leaking in from the side.
  • The longer the curtains the better.
  • Install a cornice at the top of a curtain
  • Use Velco to attach the ends of the curtains to the walls and to each other in the centre
  • Blinds do little to reduce heat loss in the winter

Draft-proofing sash windows

October 13, 2008

The two materials you will need are bristles strips, and compressive foam seals.

 

First open the window. Put compressive foam seals on the underside of the top and bottom edge of the window (Marked A). When doing this it is important that you cut the strip to the exact size required to provide as complete a seal as possible. For wider frames it may be possible to install a second layer of compressive frame seal.

Next, close the window, and fit bristle strip to both sides of the beading of the lower sash (Marked B). Do exactly the same for the upper sash BUT on the outside.

Finally to draft proof where the sashs meet (Marked C). Bristle strips should be fitter on both sides with the bristles facing each other just touching. This will stop drafts coming in the middle.


Solar Thermal Panels – Flat bed or Evacuated Tubes

June 16, 2008

Solar Thermal Panels or Solar Water Heaters come in two main types… Flat bed panels and evacuated tubes. So which are better?

Well first of all, the theory behind the two systems is much the same. See this post for more. Solar collectors (which are essentially just thin pieces of metal) absorb energy from the sun, and transform this energy into heat. This heat is then transferred to the houses hot water cylinder where it provides useful hot water.

The main difference between two technologies refers to the way the metal collectors are configured.

Flat Bed Panels are a simpler technology. A thin panel of metal, usually painted black, is positioned just below a pane of glass. The reason for the glass is to prevent heat escaping into the air, and so maximise the amount of heat transferred into the hot water cylinder.

The benefits of the system

Flat bed plates are relatively cheap

When the sun is shining directly at the panels, they have the maximum plate surface area exposed to the sun, and so achieve the maximum possible

They look very inoffensive

The drawbacks of the system

At times when they are not receiving direct sun, they’re not as effective evacuated tubes

If the panel is damaged, it will have a very significant effect on efficiency of the system

Evacuated Tubes are a more complicated technology. Thin strips of twisted metal are positioned in the centre of a vacuum filled tube. The vacuum tube means conduction losses are reduced, while the glass acts to reduce convection losses. The idea behind the twist on the metal is that it means part of the panel is at the correct angle to receive the maximum energy from the sun, and therefore providing energy to the cylinder at lower sunlight times of the year.

The benefits of the system

Provide a significant amount of energy to the cylinder at all times of year

If one of the tubes is damaged, it will have little effect on efficiency of the others. Also it is easy to change one tube if necessary

The drawbacks of the system

More expensive than flat bed systems

They are less effective during times of direct sunlight. Does it matter?

They are more remarkable looking than flatbed panels. A bad thing?


Underfloor or Rads – Heat Emitters – Heating

June 4, 2008

This is a quazzy energy question… but it comes up a bit, so…

So first, the principles. Underfloor heating and Radiators are “Heat Emitters”, which have the job of transferring the heat from the hot water, that was heated by your boiler, to the room. Rads systems generally operate using water systems at 55C. Under floor systems use water at 35C.

Installation cost

Radiators are cheap – Underfloor is expensive

Space they take up

Underfloor is out of site. Rads take up space, and some might even say are quite ugly.

Safety

Underfloor is fairly danger free. Rads are hot to touch, so might cause an accident

Heat up time – Response time

Rads can heat up a room quickly (since the water in them is hotter). With underfloor, it takes longer, so you need to have switched on the heating earlier to get the same effect (though being on for longer will not mean more cost, just longer at a lower setting)

Retaining heat

Underfloor is better for keeping a background level of heat in the house. See thermal mass

Efficiency

Lower temperature water is more efficient, so underfloor

If badly controlled, underfloor heating can be waste lots of energy, so rads

Modern Condensing boilers (the most efficient boilers available), work better with lower temperature systems, so underfloor

If properly insulated, the walls, and floor are a similar heat loss, so nothing here

Room Flexibility

Underfloor allows you to put furniture wherever you want. With Rads, that can be a problem

Rads allow you to have any floor covering you want. With underfloor, heavy carpets are a problem

Alternative technologies

Some alternative technologies, such as Geothermal Heating only work with lower temperature systems.

Future?

I think it is likely that the lower temperature thing will become bigger and bigger in the future. The hotter you need to get the water, the more challenging. So in my dream house… underfloor

Other points

Underfloor doesn’t leak (if put in correctly day one)… something which can’t be tampered with by people… is usually less demanding on maintenance. In fact… rads are more likely to leak. (just don’t hammer a nail into the floor)

Underfloor won’t burn your feet

Retrofitting underfloor = money pit


Understanding Geothermal Heat Pumps

May 3, 2008

Geothermal heating… Geo=ground… thermal=heat. Someone told me the other day that it was really hot under the ground and that’s how they worked. Well I hate to ruin this simple view, but that’s not how they work. It’s a little more complicated than that. This post gives the simple explanation, and then the physics explanation.

Simple explanation

Geothermal heat pumps use a pumping mechanism to absorb heat energy from under the ground and “pump” it into your house. The clever part is that due to a clever trick, they only use about one unit of electricity to “pump” about 4 units of heating into your house. Electric heaters use one unit of electricity to generate one unit of heating, so Geothermal Heat Pumps are 4 times more efficient. The downside is that they only work on lower temperature systems, meaning you really need to have underfloor heating to make use of them effectively.

Physics explanation

First you must realise that there is energy in everything. Once it’s not at absolute zero, it’s got energy in it, thermal energy. Next you need to have a vague understanding of pressure. In a fluid the molecules are all flying around, vibrating, that sort of thing. If you heat them up, they vibrate more, and so the fluid expands. What’s really interesting here though is that it also works in reverse. If you compress a fluid, it tries to give out heat. Similarly if you let a fluid decompress, it will try to suck in heat from its surroundings. Basically what I’m saying is that by changing pressure, you can actually make a fluid give out, or suck in, thermal energy.

That’s the key to Heat pumps. They use a loop of fluid, which is allowed to expand in one place (under your lawn or somewhere like that). It then absorbs thermal energy from the surroundings. The fluid is then pumped into your house, where it is compressed, and so needs to give out that energy. The heat pump then transfers that heat to the heating system in your house and boom!

Thanks to daviddarling.info for the pic


Understanding Wood Pellet Boilers – A simple guide

April 30, 2008

What are wood pellets?

Wood pellets are small pellets of compressed saw dust. Simply put saw dust is a by product of other more lucrative wood processing. This saw dust is dried to a specified moisture content, and compressed by a very high pressure machine. Generally no glue or binding agent is required other than the sap from the timber itself.

The benefits of wood pellets are

  • Its easy to transport
  • It is clean
  • It complies to standards. Things which have standard sizes, shaped and moisture content can easily be designed for

So these pellets, how do they get to the boiler?

No, a shovel is not required. The pellets are blown from a delivery truck up to 20m to a storage unit. In the past there has been a lot of hassle with dust, but this was largely down to the use of agricultural feed trucks being used to deliver the pellets. As dust is not really an issue for agriculture, they did not have dust minimisation technology, and it was a mess. If you use one of the large suppliers these days, there is little problem.

So the pellets are in the storage unit… what now? Well the next stage is getting it to the boiler. The simplest solution here is to use a screw system. These systems turn very slowly and draw the pellets from the storage unit to the boiler.

Understanding Wood Pellet Boilers

And.. Combustion

Combustion… Explain?

Wood pellet boilers are fed into the “burner” where they are burned. The burner in all boilers does much the same job. It’s a place where the fuel is mixed with air to provide the optimal conditions for combustion, and lit. Before you know it the combustion gases are travelling through the heat exchanger where it heats up the water.

Understanding Wood Pellet Boilers

Understanding Wood Pellet Boilers

Heat exchanger

The flame from the burner, and the resultant combustion gases escape into the boiler, transferring their heat to the water circulating through the heat exchanger within the boiler. The heat is then distributed the house using a wet system. In most cases water flows through the heat exchanger in the boiler, absorbing heat from the flam and the combustion gases. This hot water is then circulated around the house to radiators, underfloor heaters and hot water cylinders.

For more infor See  my boilers post

Thanks to

www.JFC.ie

www.ecotality.com

www.asgard-biomass.co.uk/

www.gerkros.ie

for the pix!