Two months of Solar Hot Water monitoring

October's Performance

With October done we now have a second month of data from the Solar Domestic Hot Water monitoring project.   In September we had relatively good performance with 41% of the water heating needs supplied by the solar panel.  October on the other had great sun for about a week mid-month, but then was much cloudier, shorter days and substantively lower performance.  Here is both September and October's graphs so you can compare the two months:

Again, a few observations:

1. Total energy used this month for hot water heating was up 79 kWh to 356 kWh of energy put into the heating of hot water.  Of this only 15%, or 52 kWh was solar supplied.  The higher energy use this month could possibly be explained because the basement is heated off of the hot water system.  I did observe that the basement's infloor heating system was running periodically to supply heat to the basement. 
2. The amount of solar heat collected this month was again lower than modelled (52 kWh vs. 80 kWh modelled).  Also, as a percentage, the solar fraction as only 15% which was slightly lower than predicted at 16%.  
3. The total amount of energy actually delivered as hot water was about the same as last month: 131 kWh.  September was 127 kWh, so it looks like hot water usage was consistent with last month. 

There Goes the Sun

Below is a picture of the solar collector and the sun at about noon on November 6th.  As you can see the sun isn't really clearing the trees much.  The sun now goes behind the escarpment downtown shortly after 3pm.  You can see the solar panel itself mounted on the veranda roof (behind the power pole.) So from this point forward, it doesn't like the system will be collecting any heat until February.

Why a Carbon Tax is good for the Yukon’s economy

I’ve been really confused by the Yukon Party’s opposition to the carbon tax.  It seems they don’t understand the Yukon’s economy.  It needs to be said that in fact a carbon tax will be GOOD for the Yukon’s economy.  This is for two reasons:

1. The productive part of the Yukon’s economy actually has a very low carbon intensity.  We have a highly educated workforce and most of our economy is not resource intensive.  Mining, oil & gas are only about 13% of Yukon’s GDP (see Yukon Bureau of Statistics’ Gross Domestic Product (GDP) by Industry 2014).  Because mining produces a product (metal), that actually overstates the value of the resource industry when it comes to jobs and salaries paid.  Therefore the bulk of our economy is low-carbon intensity.  With a carbon tax, the Yukon’s economy is more competitive relative to carbon-intense economies.  In other words, the Yukon will perform better relative to other provinces when carbon taxes come into play.  This is a basic of economics:  do what you are good at and the Yukon is good at having a low-carbon intensity economy.

The Yukon also has excellent opportunity to further de-carbonize our economy by increasingly switching to renewable energy (primarily hydropower, but also biomass and to a lesser extent wind and solar).  Other jurisdictions do no have the natural resources to produce renewable energy that the Yukon does.  As such, the Yukon can readily further reduce its exposure to carbon taxes and become even more competitive.  

2.       Use of fossil fuels represents a significant economic leakage for the Yukon.  In 2013 the Yukon consumed about 226 million litres of gas, diesel (inc. heating fuel and jet fuel) and propane (see Yukon Greenhouse Gas Emissions: the Transportation Sector, 2015).  If we assume this is about $1/L, that is $226,000,000 that left the Yukon with just about no economic benefit to the Yukon (we essentially burned that money).  Any reduction in fuel usage will result in more money staying in the Yukon’s economy and can be put to more production use.  For example, the money could be used by Yukoners for arts, entertainment, culture, health care, education or just about anything will be more useful that burning the money.  This will also help build the local economy since more resources will be used and consumed locally.  Even a 10% reduction in fuel usage will be $22 million dollars that would be repatriated to the Yukon’s economy.  That is almost exactly at 1% increase in our GDP which would have wiped out the GPD decline the Yukon experienced in 2013 and 2014.  

Another thing that makes me mad is the rhetoric does not reflect the realities of math.  The carbon tax will have almost no measurable impact on the price of goods (and zero impact of the cost of services) because the amount of fuel used to transport goods to the Yukon is very very small relative to the value of the goods.  Where you will see the difference is at the gas pump and on heating fuel.  But it is not much of a difference:  the $10/tonne tax will be about $0.02 /L at the pump.  Yup, that is it: less than the price difference between gas stations and less than the difference between regular and premium.  If you drive the speed limit and drive conservatively, you will increase your fuel economy by 10% which more than offsets the fuel price increase of 1.7%.  Any driver can fully mitigate the any fuel price increase. 

First month of Solar Hot Water monitoring data

With the end of September we now have our first full month of energy monitoring data for the solar domestic hot water (SDHW) at 704B Wood Street (see http://forestpearson.blogspot.ca/2016/09/solar-domestic-hot-water-monitoring.html for background).

Since September is an equinox month (average day/night) we can kind of assume it is representative of annual average sunlight.  So it is fortuitous that the first month of monitoring has been September as it gives us some indication of what annual performance might be. 

And the result?  Significantly less saving than predicted by the energy model.  The interesting thing is it does not seem to be due to system performance (which is performing better modeled), but due to a more insidious factor:  Conservation!  Basically the residents of the home are not using enough hot water to realize the potential of the system.  This is because there are a number of hot water saving measures designed into the house (including a very large drain water heat recovery system), that there are only 2 to 3 occupants in the house and lastly the residents are very energy conscience and therefore don't use a lot of hot water.

The first rule of energy conservation wins yet again:  reduce the consumption first before looking at efficiency, and only then (last) is renewable energy generation (which is what the SDHW system is.) 

Below is a graph of September's energy performance of the system. I'll explain the three bars and the preliminary findings below:

1. The first bar on the left is the predicted hot water performance from the HOT2000 building energy model.  The model suggested that water heating in September would take 487 kWh of which 34% would be supplied by the solar system.  I don't know the details of what and how the model works, but I do know a few of the assumptions that help explain the difference.  HOT2000 standard reference defaults to assuming there are 4 people in the house (2 adults and 2 children).  It assumes they use 225 L of hot water a day at 55degrees C.  In the actual home there are 2 to 3 adults, they only use 125 L/day and the tank temperature is maximum 45degrees C.  So on water usage alone this house uses 44% less hot water than the model.
2. The middle bar is the actual total energy usage of the hot water system.  In September a total of 277 kWh of energy was put into the hot water system, of which 41% was supplied by the solar system.  Therefore we see 43% less total energy input, which matches well with the reduced hot water usage recorded (versus the model).  But we did see in September 2016 that the solar contribution at 41% was substantively higher than that modelled.  
3. The last bar (on the far right) is very interesting:  this is the amount of energy that actually supplied hot water to the tap.  The difference between this and the middle bar is energy lost as heat leaking off the storage tanks.  What we see here is only 131 kWh was used (of which 47% was solar supplied) to make hot water.  The remaining  146 kWh was presumably heat loss off the two big storage tanks.  Normally this would be considered "bad", but in the case of this super-insulated home, this might not be so bad.  This is because the house is electrically heated and with the high level of insulation, much of the "waste" heat off the tanks will be retained by the house.  This then displaces electricity that would be used to heat the house.  Of course, in the summer there really isn't any heating needed, plus the tanks are in the basement, a location that doesn't need to be as heated.  But none the less, the heat loss off the storage tanks isn't a total loss. 

Preliminary Findings

After one month of monitoring, it appears that the savings from the solar domestic hot water system are substantively lower than predicted.  This is not due to system performance, but due to low demand for hot water. 

Because this home is primarily in "first block" power (< 1,000 kWh/month), the electrical rates are quite low and therefore the savings (displaced electricity) are low.  At this time, first block power is approximately $0.109 / kWh.  At this rate, the solar system only saved about $12.49 in the month of September.   If that is representative of "average" savings, the total annual savings from the system are only about $150/yr.  That means it will be a very long pay-back for this system at these low electrical rates.

What I conclude from this is the solar hot water system seems to work well with good performance, however its value in a small, high-efficiency home, is low.  It is a technology that would be better suited to large homes with higher hot water demands or commercial/institutional buildings with large hot water demands. 

But, let's see how the rest of the year goes.

Solar Domestic Hot Water Monitoring Project

© Richard Legner

We included a domestic solar hot water (DSHW) system when we built our SuperGreen Laneway house back in 2014.  There is no known real-world performance data on these systems in the Yukon.  In partnership with City of Whitehorse, Energy Solutions Centre and Yukon Housing Corp we have installed a monitoring project to establish actual energy savings of the system.  The data is near real-time (updates ever two minutes - refresh your browser).

The monitoring system was commissioned on September 1, 2016.  You can view the data at:

http://www.welserver.com/perl/view/5153

Good documentation of the various data fields is found at: https://www.halifax.ca/solarcity/Other/documents/WELServerPPTv30.pdf

Two summary monitoring reports will be prepared as part of this project: one in March 2017 and a second at the end of 2017.

Background & Project Objectives

Solar domestic hot-water (SDHW) heating is a building-scale renewable energy opportunity that has had limited application in Yukon to date.  It is an established and reliable technology that has the potential to further reduce the environmental footprint of Yukon buildings; in particular, residential buildings.  However, there is no known actual real-world performance data for this technology in Yukon.  This monitoring system is the first to systematically monitor the actual performance of the existing new SDHW system at 704B Wood St. in downtown Whitehorse. 

Photovoltaic (solar electric) technology has as relatively good uptake in the marketplace and PV performance is relatively easy to monitor.  Conversely solar-thermal technology has had much lower installation rates in spite of its relatively higher efficiency of conversion of solar energy to heat.   This lower rate of uptake is thought to be due to four factors: 

1. lack of demonstrated performance of the systems in the Yukon environment; 
2. perception of higher capital costs relative to PV; 
3. lack of skilled trades and contractors supplying and installing the systems; and 
4. limitations created by ability to utilize the energy based on building hot-water demands. 

The project looks to address the first barrier to uptake:  demonstration of performance.  

It is believed that there is place for solar-thermal in the increasing energy efficiency of Yukon homes and buildings because of the technology’s relatively higher efficiency for generating thermal energy and the 5 kW installed capacity cap on PV created by the Yukon’s Micro-generation program (solar thermal can be installed in addition to PV).

Existing System

© Richard Legner

The SDHW system at 704B Wood St. is a single flat-plate collector system installed in late 2013.  The system is a Thermo Dynamics CSA-certified“Solar Boiler” hot water heater installed on a two-bedroom single detached home.  A unique feature of this home is the basement is heated by an in-floor hydronic system supplied from the home’s hot water system.  The purpose of this configuration is potentially increase the solar fraction provided by the SDHW by using the basement concrete slab as thermal storage of solar-derived heat.  

One year (almost) of energy use data from our new SuperGreen home

Below is a chart summarizing actual month energy use data for the last year from our new SuperGreen Laneway Home in downtown Whitehorse.  This home is rated as an EnerGuide for Homes rating of 89--just about the highest so far for the Yukon.

The graph shows in blue total actual energy use (electricity because the home is electrically heated too) and in red is the predicted energy use from the energy model created when the house was planned and built.

Since winter 2015-16 has been unusually warm I've "normalized" the actual energy use data to average winter conditions.  That way it takes out the effect of a warm winter.

Also I've adjusted the modeled energy use data for one occupant.  The "standard" conditions used in the EnerGuide rating assume a family of four.  So, I took that out of the model to better compare apples-to-apples.

What this shows is this house too is performing better than expected.  Overall, it has used 19% less energy than the model predicted.  This is a similar result to our SuperGreen duplex built in 2011 that uses about 30% less than predicted.

A few interesting things in the graph for 704B Wood St above.  You can see energy use "spike" in November and February.  In both of those months the garage was heated and "occupied".  In November my friend used the garage for about two weeks as a framing shop; and then in February Georgi and her friends setup a pop-up craft shop for a week.

I was worried this house was using more energy than predicted, but now that I see all the numbers in, I'm pretty happy with the results.