我们之前的更新涵盖了建筑围护结构的各个方面，这使我们能够将每年的供暖需求降低到大约每平方米15千瓦时的被动房标准。窗户是其中的一部分，也是我们能效战略的一部分。
The house is laid out south facing to maximize passive solar heat gain, so we have designed and chosen windows to take best advantage of that.
北部、东部和西部的窗户玻璃的R值为8.4，但南部故意只有R值6.4，这是由于不同的低E涂层。低E涂层减少热损失，但也减少热增加。通过牺牲南侧30%的隔热值，我们可以增加80%的被动热增益。
In houses that perform at this level of efficiency, domestic hot water becomes the single biggest consumer of energy. To tackle that we have two heat pumps that together will drop that demand dramatically.
A Mitsubishi 'Mr. Slim' split heat pump will provide heat to the house; we also have a heat pump water heater from AO Smith. The Mr. Slim operates efficiently down to -25 celsius at close to a 3 to 1 ratio of consumption, meaning 3 units of heat out per unit of energy in.
这比只有1比1比例的标准电热脚板加热器的效率高出三倍。来自AO Smith公司的Voltex热水器是一种空气-水热泵，它从空气中提取热量产生热水，因此在冬季，第一台热泵的3比1加热比被转移到热水器中。
和the more 'free' heat you have in winter (solar gains and general occupancy) the more efficient it becomes. In summer it acts as an air conditioner while it extracts heat from the air to generate hot water, in a way giving you 'free' hot water, since rather than ejecting heat from your home as most air conditioners do it is retained in the form of domestic hot water.
Since 2/3rds of the bulk energy consumption in a home is usually a result of heating, with our building envelope we've been able to reduce that to about 10 percent of what most new homes require. Beyond that, the next big leap in efficiency comes from reducing interior loads. Heat pumps are a great way to do that, particularly with hot water.
Our heat pump combination is together surprisingly affordable, and it has taken a big chunk out of the total energy consumption needed during the operation of the house.
We also have a guide page on theair-to-water hybrid electric heat pump hot water heaterthat borrows that efficiency and significantly cuts the energy required to meet our domestic hot water needs.
Now you knowmore about heat pumpsand how they work best in tandem, learn about otherefficient home heating solutionsin the following pages and in the EcoHomeGreen Building Guide.
Find more aboutgreen home constructionand reapthe benefits of a free Ecohome Network Membership here. |
Please fact check my arithmetic:
Say the external air heat pump averages a COP of 3 during the winter, and the water ASP averages a COP of 6 (since it is working with ~ 20C air.) To bring 6 kWh of energy into the home, two kWh of electricity is consumed. To move those 6 kWh into the water, another kWh of electricity is consumed. So it took 3 kwh of electricity to move 6 kWh of heat into the water, for a system COP of 2.0
I realize that the interior water ASP will shine in the summer; I'm just wondering about the winter calculation.
Thanks!
Eric