Our news April 2009 Page 1/6 Beyond small air-conditioners what?
Heat
For bigger applications as the heating of an entire house up to large buildings other types of heat pump exist suitable to cover any requirement.
pump applications There is a way to take heat from the air and the soil during the winter to keep our houses warm with much lower cost then oil or N.G.
It is sounds as a paradox or even “late night TV marketing” but it is a very real option with the use of heat pumps. Another very scientific term, but into practice is the right terminology for the commonly used air-conditioning machines of all sizes. Heat pumps are machines which as their name very clearly says, they draw heat a medium (air, water, etc) and transfer it to another medium. As an example our humble air-conditioner when it functions in the heating mode it draws heat from the environment. Heat pump for the If we feel the air that passes from heating/cooling of a the exterior unit we will realize small office building that it gets cooler. This heat is transferred into our house. The same machine the summertime “sucks” the heat through our house and rejects it to the environment (the exterior machine heats the air).
In houses and apartment buildings, normally air -water heat pumps are used, meaning they draw energy from the surrounding air and heat the water that goes in underfloor or fan coil systems. Heat pumps can replace completely the oil/gas boilers with important advantages,
There are no negatives? Of course there are, like every technical solution,
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Economical to run — up to 70% less annual cost! The offer heating and cooling so no extra AC units are needed as is the practice now. They do not need a chimney, fuel tank, or machine room. You pay the fuel (electricity) after using and not in advance. Reduced environmental pollution. Safe operation without flammable fuels, special fire protection measures, etc. Reliable solution with low maintenance requirements. Less dependence on fossil fuels.
Larger initial cost then the equivalent oil boiler so their dimensioning must be without excesses. Their efficiency is reduced in very low/ high temperatures so they study must take it into account. The design of the system has more variables. They can not be used efficiently with radiator panels.
THEROS Ο.Ε. Registered office: Ι. Karavela, Perivolia, Lefkada 31100 Tel. 26450-22299, Fax 26450-22208, email info@theros.gr
Our news April 2009 Page 2/6 Heat pumps can considerably reduce the cost of heating and the pollution of the environment An important advantage of heat pumps is that the useful energy they offer is multiple of the energy actually consumed. So with 1 unit of electric energy they offer us 2 to 6 units of heating! The COP factor indicated on their leaflets is the proportion of useful heat to the electricity consumption. Larger COP values mean higher efficiencies.
Geothermal heating / cooling
There is a lot of hype about it lately. The central machine is a heat pump however instead of using the surrounding air as a medium, it is using the ground. On such heat pumps the water replaces the air and we can get it from ground wells or pass it through piping buried in the ground. The earth 1-2 meters below the surface has a relatively stable temperature all year, around 10-15°C. So the high efficiency of the heat pump can be maintained even in conditions of extremely low or high temperatures.
Air-conditioners designated energy class A have COP equal or greater then 3,2. High efficiency air-conditioners and heat pumps have COP that can reach 6. In other words very low electricity consumption..! The E.U. has officially declared that high efficiency heat pumps are classified as a Renewable Energy. This means that buildings that include them shall have a positive grading on their Energy Certificate which will play an important role in the future.
Theros Ο.Ε. cooperates with the following companies for heat pumps,
Geothermal systems have the advantage of high average efficiency (their COP is normally between 4 and 6) so lower annual consumption but their initial cost is much higher due to the required drilling, excavation, piping costs, etc. The closest «competitor» of geothermal systems is the new generation of high efficiency air heat pumps that approach or equal the heating efficiency of geothermal systems with much lower investment cost. (an example of such an application follows) The engineer must evaluate a lot of factors to decide if a geothermal system is “worthy”, especially is areas with mild climate.
Geothermal heat pump by Vaillant
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THEROS Ο.Ε. Registered office: Ι. Karavela, Perivolia, Lefkada 31100 Tel. 26450-22299, Fax 26450-22208, email info@theros.gr
Our news April 2009 Page 3/6
Hybrid heating system with an air heat pump and oil
System selection A heat pump was necessary since cooling for the summer was on of the requirements for the new system. However, the large heating demands would require a very large heat pump with similarly large purchasing cost.
boiler Last November a large villa in the North coast of Lefkada needed the urgent replacement of its oil boiler Even though the heating system had been constructed only 4 years ago, there were basic mistakes that lead to catastrophic corrosion of the oil boiler and annual oil consumption that reached 5.000 liters! Luckily the house has underfloor heating in all spaces so we had several options for the improvement of the heating system.
As one can see from the above diagram even though the heat demand (yellow line) increases at low temperatures the heat pump (blue line) at the same time reduces its heat delivery!
The thermal study showed that the house due to its size, Northern orientation and large openings to the same direction has high heating demands that can reach and exceed 30 kW. For the same reasons in the summer it is relatively cool and the cooling loads are not more then 15 kW.
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In Lefkada the average winter temperature is 912°C. So if we selected the heat pump based on the lowest winter temperature (-5°C) we would have a very large & expensive machine which would work on minimum load for the majority of the heating period. We decided to use a combination of a high efficiency heat pump with oil boiler. This way the cost of the conversion was kept at reasonable level and at the same time we achieved the key targets of economical operation, summer cooling, and uninterrupted operation of the heating system since the house was occupied at all times.
THEROS Ο.Ε. Registered office: Ι. Karavela, Perivolia, Lefkada 31100 Tel. 26450-22299, Fax 26450-22208, email info@theros.gr
Τα νέα μας Our news April 2009 Page 4/6 System design The combination of a heat pump with a boiler is not a novel idea, indeed Daikin also mentions it on its leaflets.
As shown by the above chart Daikin recommends the operation of the boiler only or the only the heat pump depending on the temperature of operation. If we followed this system on our case we would need to operate only the boiler whenever the temperature is below 10°C (equilibrium point). The difference in the hybrid system that was chosen is that the 2 machines are always on standby and can operate simultaneously when needed. The priority however, is always given on the heat pump. The oil boiler will ignite only if its electronics sense that the heat pump can not cover sufficiently the heat demand by the house. The heat pump operates at all temperatures and the oil burner acts as a supplement for the extra energy needed.
Heat pump
Oil boiler
On the above diagram the advantage of parallel operation is clear. The heat pump (brown color) contributes the major share of the needed energy even below 10°C. The result is that the heat pump even though it has a relatively small power rating, it covers approximately 75% of the total annual heat demand. In fact because it will operate on mild temperatures (the oil burner takes care of the «rough times») the expected average annual COP of the heat will be 4,4 according to the Daikin technical data. Even geothermal systems can hardly achieve better performance but if so, with much higher cost and disturbance of the building site. In addition the new oil boiler will be used on its most efficient area of operation and only when needed, avoiding unnecessary startups and consumption. The expected reduction of heating oil consumption is 80-85% while the total operational costs will be about 65% less compared to the original system.
Building heat demand
The complete process is automatic and based on the fitting of the heating curves and hydraulic layout that was used.
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THEROS Ο.Ε. Registered office: Ι. Karavela, Perivolia, Lefkada 31100 Tel. 26450-22299, Fax 26450-22208, email info@theros.gr
Our news April 2009 Page 5/6 Planning & construction An important factor on the planning and realization was that heating should remain operational at all phases and the new system should be adapted to the existing without disturbing the interior of the house. At the first phase the destroyed oil boiler was removed, and a new high efficiency Vaillant oil boiler was installed and connected urgently in order to heat the house. The special type of cast iron and their design, allows to these boilers to operate with water temperatures down to 38°C achieving high efficiencies 94-96% without corrosion risk. The interior unit of the heat pump, the electrical switchboard with the automations, and the 3-phase energy meter
The oil boiler controls with the temperature compensation panel
On the second phase, the heat pump was installed and was test-run in combination with the new domestic hot water tank, and the automations. On the third phase, having tested that each component works as expected, the old system was completely removed, the heat pump connected with the rest, and the system finally took its designed form. The relatively cold April allowed us to see the system working to warm the house and performing as expected.
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The exterior unit of the heat pump, type Daikin Altherma
We have installed meters for the consumption of electrical energy and hot water so in the long term we can monitor if the efficiency of the system meets the expectations.
THEROS Ο.Ε. Registered office: Ι. Karavela, Perivolia, Lefkada 31100 Tel. 26450-22299, Fax 26450-22208, email info@theros.gr
Our news April 2009 Page 6/6
Annual results of our solar heating system The system which we have installed on our offices has now completed 5,5 months of operation and some conclusions can be made. The period of measurements is from December 1st 2008 until April 24th 2009, so 145 days. The heated space is 110 m2 and operates as exhibition and office space. The solar system and pellet stove heat our underfloor.
The distribution of heat by the solar system (yellow) and the pellet stove (brown) from December to April
The total consumption of pellets was 320 kg, equivalent to approximately 138 lt. of oil. If we did not the above system, with a high quality oil boiler we would have used approx. 422 lt. of oil. The solar system operated for 769 hours during these 145 days producing 2503 kWh of thermal energy. In total, solar heating covered 65% of our heat demand.
The 4 collectors that heat us
Good enough result for what was according to many locals the «the most cloudy & rainy winter of the last 20 years». On sunny but cold days even with low temperatures (below freezing in the night, less then 10°C in the day) the solar heat covered completely the demand and we did not have to light the stove at all. In the future we want to improve the automations of our system, and try different collector types.
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THEROS Ο.Ε. Registered office: Ι. Karavela, Perivolia, Lefkada 31100 Tel. 26450-22299, Fax 26450-22208, email info@theros.gr