热泵:地源地源热泵或空气源空气源热泵，哪一个是最适合为家庭供暖?

Air Source Heat Pumps, and are Ground Source Heat Pumps "Geothermal?"

First let's clear up some confusion on terminology regarding heat pumps- search Google forGeothermal Heating Systemsand you will find hundreds maybe thousands of companies using the word "Geothermal" to describe ground source heat pumps, two systems that have only one thing in common: they sit on and in the ground. Evengovernment organizations把它们叫做“地热热泵”来搅浑故事。

Real Geothermal systems直接从温泉、间歇泉和火山热点等自然资源中使用热量，在美国和加拿大，只要这些条件存在，这是一种遥远的可能性。

Ground source heat pumps或地源热泵是使用地下水或简单的土壤来冷却冷凝器的空调，而不是外部盘管和风扇。它利用电能将热能从它不想要的地方泵到无关紧要的地方。倒着运行它，它就能泵出热量，比直接使用电力更有效，通常用COP等级(性能系数)表示。

所以，我们在这里研究的绝对是地源热泵和空气源热泵性能的比较——而不是真正意义上的“地热”供暖——但是，嘿——正如许多人所说的那样，他们也会去搜索它，对吧?

GSHP's v ASHP's - how are they compared?

The Sustainable Technologies Evaluation Program (STEP)is run out ofThe Living City Campusat Kortright, ON, where you can findThe Archetype Sustainable House (ASH). The two houses act as a living laboratory with more than 400 calibrated sensors that monitor the performance of the buildings' systems. There is also an on-site weather station measuring outdoor meteorological conditions, providing site-specific climate data.

Much research has been conducted through the STEP program, ranging from low-impact development storm water management to energy efficiency and renewable energy research. Ecohome will summarize and deliver this valuable information to our readers.

Quite often there is a chasm separating those conducting research from those in the field who would greatly benefit from the research conclusions and we are hoping to bridge that gap. This first study looks at two forms of heat pumps; ground source and air source.

Zuba Central air source heat pump © Sustainable Technologies Evaluation Program

Heat pump technology is evolving rapidly, causing energy-savvy builders to take notice as the technology improves and the prices come down. If you are unfamiliar with how a heat pump works, imagine a refrigerator; it doesn't 'create' cold, it simply condenses heat on one side of an enclosure and moves it to the other side. The heat is released through coils on the back of the fridge and warms your house a little bit in the process, which is the same process that is happening with an air source heat pump (ASHP) sitting inside or outside your home. "Heat pump" is the pertinent part of the name here - these systems basically pump heat around from where it isn't wanted to where it is, or where it doesn't matter. This is why there exist so called split systems, as these can both heat and cool - depending which way the pump is running.

乍一看，用寒冷的冬季空气给房子供暖似乎是违反直觉的，但只要温度高于绝对零度(-273°C)，就有一些热能存在。没有空气交换发生从内到外与空气源热泵;当室内空气通过加热的盘管循环时，热量在室外简单地凝结，在室内分散。在夏天，这个系统反过来给你的家降温。

WaterFurnace ground source heat pump © Sustainable Technologies Evaluation Program

地源热泵(GSHP)在相同的原理下工作，从地面提取热量，然后用于为家庭供暖。这就是地热加热的简单概念。地源热泵也反过来为您的家降温，这是系统效率的一个重要因素——在夏季为您的家降温的同时，您正在为下一个供暖季节加热地面。Whichever system you choose - air or ground source, condensing and moving heat from one place to another is much more efficient than generating heat and that is the reason that heat pumps are a hot topic inthe performance building community.

What we will cover here are the conclusions of a comparison between ground source and air source heat pumps, in terms of overall cost as well as efficiency in performance to ascertain which is the best.

Mechanical heating systems being tested:

House A

Heated with a 10.5 kW (3 ton) high-efficiency variable capacity air-to-air source heat pump manufactured by Mitsubishi™ with a direct expansion coil air handling unit (AHU) and a multi-speed fan to supply warm and cold air for space heating and cooling.

House B

通过WaterFurnace™生产的13.3 kW高效地源热泵加热，并连接到院子里两个152.3米(500英尺)的水平回路。

Ground source heat pump vs. air source heat pump

What is interesting to note right from the beginning, is that during testing, both heat pumps as stand-alone units (i.e. not including circulator pumps or blowers) actually exceeded manufacturer and EnerGuide ratings, with Coefficients of Performance (COPs) above 5 in the cooling season and above 3 in the heating season.

Disregarding installation costs for the moment, here is what that would mean on a monthly utility bill - conventional electric resistance heat (baseboard heaters, boilers, toasters, hairdryers, etc.) has a COP of 1, meaning one unit of electricity produces one unit of heat.

So, a COP of 3 means you are getting three times more heat for every dollar you spend with a heat pump compared to a normal electric heater. Air conditioning units typically have a COP of between 2 and 3, so if a heat pump in cooling mode has a COP of over 5, you could reasonably expect to cut your operational cost in half compared to a dedicated A/C unit.

There are other factors at play that may lower efficiencies and some system configurations that could increase efficiencies, but we will stick to the basic performance here. Greater details can be found in thefull technical brief.

在所有季节，空气温度的变化比地面温度大得多，所以地源地热系统有一个明显的优势，即更可预测和一致的操作条件。这一点在测试中得到了证明，冬季气温下降对空气源热泵性能的影响比地源热泵更严重。然而，在没有补充热量的情况下，空气源热泵在室外温度低至-24°C时仍能保持室内热舒适。地面温度不会低于地源热泵的工作温度，因此，假设系统的大小与它所需的加热空间相适应，你不需要补充系统。

所以，关于空气源热泵，这就引出了一个问题:在-25°C或更低的温度下会发生什么?在历史上，这一直是一个问题与空气源热泵作为唯一的热源在寒冷的气候。有一天当你最需要它的时候，它可能不会提供热量。就在不久之前，情况甚至更糟，当时它们只能在零下10摄氏度左右工作。If considering an off-grid home running on solar panels and batteries, or for backup heat "just in case" or in the case of a prolonged power outage, perhaps consider ahigh efficiency electricity free wood pellet stove designed for off-grid use, see here.

In this test case the system was coupled with a backup mini-boiler to supply hot water to the heating coil of the Air Handling Unit (AHU) when the ASHP was unable to. The system would heat less efficiently with the boiler rather than in its heat pump mode (as the COP drops to 1 like any other electric heater) but at least you have heat when you need it. And days that cold are not very common except in the far north, so for the vast majority of time in the most populated areas of Canada or the USA, a hybrid system like this would run in its efficient mode.

Worth noting is that testing was only conducted with the system operating in heat pump mode, not with the electric resistance boiler. The Living City Campus where testing was conducted is in the Greater Toronto Area, sort of a middle ground climate for Canada. Model simulations for five major Canadian cities showed that both technologies can perform well in the Canadian climate and should also perform well across the colder States of the USA. Another thing to try if in a cold climate zone is aDIY solar air heater - see here.

Temperatures affect heat pump efficiency

The efficiency of extracting heat from cold air could be compared to that of squeezing a damp sponge to get water. The less moisture there is in the sponge, the harder you'll have to squeeze. So, the colder the air is, the more energy it takes to squeeze the heat out.

The average COP of the air source heat pump over the heating season was 3, but its actual efficiency varied, dropping from a COP of 4.9 to 1.6 as outdoor temperatures fell from 9˚C to -19˚C during the winter.

The consistency of ground water temperatures means the efficiency of GSHPs fluctuate much less than ASHPs, and over the testing period it was found that the GSHP did perform at a slightly higher overall efficiency than the ASHP, but don't let that fact alone make your decision; there are far more variables to consider.

Choosing a heat pump

In colder environments a ground source heat pump operates more efficiently than air source, but the ground is not as easily accessible as air. Either you will need boreholes drilled, or if you have a large chunk of land you can dig a deep trench and install a horizontal loop. However, both of those options are very expensive. So in climates where either type of system can provide heating and cooling for most or all of the year, the ASHP has a distinct cost advantage.

房屋大小是另一个重要的变量，特别是与地源。当服务于更大的空调空间时，地源热泵的前期成本变得越来越具有成本效益，因为该成本在总建筑预算中所占的比例越来越低。而且，把大额账单减半比把小额账单减半能节省更多的钱，而储蓄决定了回报期。

Another consideration while prioritizing components of a building budget, is the idea of diverting money away from heat generation and more towards heat retention; meaning, spending more on insulation can result in needing to spend less on heating infrastructure (not to mention significant operational savings as well). Extra insulation is always the route we would suggest first, andwhich types of insulation, how much, and where to use it is covered here.

Losing less heat means you need to add less heat, so with some foresight in the design phase you may be able to meet your heating needs with a more compact and affordable system.

This particular variable scores a point for air source only, not ground source. You may be able to downsize to a smaller ASHP, but there is simply no way around the enormous costs associated with boring holes or a massive excavation undertaking for a GSHP horizontal loop.

General conclusions: air source heat pump v ground source heat pump

There is no single right answer in deciding which system is more cost effective for consumers. You'll need to weigh the variables yourself in making that decision. But as a general rule - GSHPs may be better for very large homes and those in very cold climates. ASHPs are definitely more cost effective in small, efficient homes and any moderately sized home in temperate climates.

ASHPs have a lower capital cost but there are also other important considerations here that are not always reflected in a simple payback analysis. For example, the ground-loop of a GSHP is claimed by manufacturers to last upwards of 50 or even 100 years and throughout its long lifetime will offer a better source and sink for heat energy.

Also, in an urban context, ASHPs reject heat to the outside air during the cooling season, potentially worsening the urban heat island, while GSHPs reject heat to the ground to be stored for the next heating season. The shared social good of a GSHP in this context is without a doubt real, but would be difficult to monetize.

安装空气源热泵系统的初始成本可能比电炉或煤气炉高一点，但你会每月收回一些额外的投资。回报期很大程度上取决于你所在地区的电价，这在加拿大和美国的不同省份有很大差异。在撰写本文时，魁北克水电的基本费率为每千瓦时5.4美分，安大略高峰费率有时难以计算，但高达每千瓦时17.5美分。

在许多司法管辖区，最具成本效益的空气源热泵技术的使用是翻新现有的电加热建筑物。这将立即将每年的取暖成本削减3倍，并提供非常有吸引力的回报。

Research has shown that heating a single family home with a heat pump instead of a natural gas furnace or boiler yieldscarbon emissions savings comparable to taking an average car off the road.

A gradual transition to heating with heat pumps offers benefits beyond simply economic incentives for system owners. As governments at every level are beginning to get more aggressive about combating the threat of global climate change, transitioning to more efficient heat sources is a painless way to help meet carbon emissions targets while also reducing environmental damage from resource extraction.

To世界杯2022赛程时间表最新 , from the EcoHomeGreen Building Guides