Cordless yard tools

Someone who does not know me well asked me by email if I could repair the engine in her weed wacker.  I bit my tongue and politely replied that I don't use gasoline powered yard tools and would not choose to repair one even if I could.  I urged her to see this as an opportunity to go cordless and reduce pollution and emissions.  

The EPA says that: "A conventional lawn mower pollutes as much in an hour as 40 late model cars for an hour."  Plus I don't like the stink of gasoline or the awful noise.  Cordless yard tools are now in their prime and very affordable.  You can buy them at almost any hardware store.

Shown above are my Black & Decker 20 Volt cordless hedge trimmer, weed wacker and my home made monster lawn mower.  The hedge trimmer I refer to as a "Light Saber" - I can just wave it near anything less than 1/4" and it cuts right through without slowing down a bit and can chew through up to 1/2" branches.  The weed wacker is also very powerful.  Both tools last over 20 minutes on a charge which is plenty for home use.

Back in 2005 when I built my cordless lawn mower, there weren't many options for cordless lawn mowers, but they are common now thanks to advancing lithium battery technology that has driven the costs down dramatically. 

If you are a curious/nerdy person, you can read about my electric lawn mower construction in my detailed blog: http://www.arttec.net/Solar_Mower/index.html  It was featured in Popular Science Magazine in July 2008 and I inspired several people to do similar conversions of lawn mowers.  Mine is very powerful and can charge through tall grass with impunity!  It has a 22" cutting path while cordless models range from 14" to 21".
 
Popular Mechanics recently reviewed 6 best cordless lawn mowers for around $500.  Read the full review here.  Or this excerpt:
 "The benefits of a battery mower are obvious from the moment you engage the operator lever: They’re incredibly quiet. Gas-engine mowers succeed because they produce so much power that they can afford to waste most of their output as noise, heat, and friction. With battery mowers, that output occurs at the power plant, not in your yard. These mowers are also mechanically simple. There’s no electric start or recoil start, either—just push a button to power it up. Like any electric machine, basically it’s on or its off. There’s no engine oil, spark plug or air filter to change. Keep the battery charged and sharpen the blade. That’s all there is to it. As with cordless power tools, you charge a battery separately from the tool or machine, which allows you to simply swap out the battery when it’s dead and to keep on working."

Geothermal energy for the future!

Av Henrik Holmberg, stipendiat ved Fakultet for ingeniørvitenskap og teknologi, Institutt for energi- og prosessteknikk, NTNU

Geothermal energy has received increasingly international interest during the recent years. One example of this is the yearly geothermal conference at Stanford University in USA where both the number of publications and participating countries has increased rapidly during the last 5 years. Geothermal energy is commonly used both for heating demands and for electricity production and the theoretical potential is enormous. In a MIT-rapport from 2006 it is estimated that the resource can contribute with up to 100.000 MW electricity in USA within the next 50 years [1].

Geothermal energy referrer to the thermal energy that is produces in earth’s crust through breakdown of radioactive isotopes and the heat that is transported outwards from earth’s interior.  The concept geothermal energy includes both deep geothermal energy systems where heat is mined from depths of several kilometers and shallow geothermal systems where wells with depths of a few hundred meters are used in ground source heat pump (GSHP) systems. While shallow geothermal energy is indeed an important part of the geothermal sector, deep geothermal energy is the focus for this text.

Deep geothermal energy has long been tightly associated with the geographically constricted and naturally occurring hydrothermal systems in volcanic active regions, see figure 1. In recent years it has been pointed out that engineered geothermal systems (EGS) can provide a way for geothermal energy to grow outside its geographical constraints and thereby to reach a significant share of its huge global potential. 

Figure 1. Manifestation of hydrothermal system in Iceland.

The research on EGS or, hot dry rock (HDR) systems as it was first named started in the seventies.  Primarily sedimentary basins and the periphery of the active regions were of interest in the subsequent projects aiming to extract heat from 4-5 kilometers depth through artificially created or stimulated fractures. A milestone was reached in 2006 when electricity production could be started from a research project in Soultz, France. Since then, commercial companies have been joining the field, and amongst others, USA and Australia have invested significant amounts into the research and support of geothermal energy. 3^rdof may this year,  electricity production started at the commercial EGS power plant in Habanero, Australia [2], where heat is extracted from a sedimentary basin. Although these pilot-plants have a relatively low power output in the range of 1 MW_e, they are important proofs to the validity of the concept with artificially created geothermal systems.

Geothermal energy is ideal as a base load resource for direct usage of heat. Through history, geothermal energy has been used to cover direct heating purposes such as space heating, bathing and agricultural demands. In the development of EGS it is electricity production that has been in focus and thus areas with the highest geothermal potential have been sought.  While low temperature resources that can be exploited for direct heat-purpose have been neglected for some time.  This was recently pointed out in the IEA- roadmap for geothermal energy [3], which urges countries to also asses their potential for low temperature applications.

Low temperature resources can as well be used to produce electricity with binary cycles at temperatures lower than 100 º C. This has much in common with heat recovery from low grade waste and the efficiency for such a process is bounded to be low by the laws of thermodynamics.  Thus electricity production would only be considered if there were no other way of disposing the heat, or in remote locations outside the electricity grid. Trough direct use of geothermal energy a high efficiency is ensured, while the resource can be used to displace for example electric resistance heating or other high grade fuels that could be used for electricity production.

District heating provides an ideal way to distribute low grade energy. And it accounts for 85 % of the direct use of geothermal energy worldwide [4].  The stable nature of geothermal energy makes it a suitable base load candidate in a district heating grid. However, district nets often operate at excessively high temperatures. In Scandinavia it is common with production temperatures around 80-90 °C and return temperatures around 65 °C.  In some systems even higher temperatures can be found.  High temperatures are often related to requirements from industrial processes while domestic consumers in general have a significantly lower temperature demand. Future district heating nets are likely to be operated at lower temperatures as the heating demand of buildings decrease; this also reduces transmission losses and promotes renewable energy resources such as solar and geothermal.

The primary focus of my research is an EGS in which the heat transfer is based on primarily thermal conduction [5]; in theory this gives a reliable system with a predictable long term performance. The amount of energy extracted from the system is, however, in direct proportion to the potential between the temperature of the inlet fluid and the targeted reservoir temperature. Thus a shift towards lower temperatures in district heating can have a tremendous impact on the accessible geothermal potential.  Even though the geological conditions in Norway are less favorable compared to other places where EGS projects have been initiated,  an EGS could be built based on what is considered accessible depths (4- 5 km) to provide hot water in the temperature range of district heating.  

The geothermal sector in going through an expansive phase, currently it is the shallow geothermal installations that grow fastest while the knowledge base is being build up on deep geothermal and EGS.  The potential for EGS is, however, tremendous, and the development is driven forward with successful projects like the ones mentioned earlier. In a world craving for energy, geothermal energy could be one of the major players and EGS is probably the way to unleash the potential. It remains however, to be proven that the installations can sustain long term heat production and that the concept can be applied to a variety of different site-conditions.

References:

1. http://mitei.mit.edu/publications/reports-studies/future-geothermal-energy, accessed 20-06-2020

2. http://www.geodynamics.com.au/home.aspx, accessed 20-06-2020

3. IEA 2020, http://www.iea.org/publications/freepublications/publication/name,3988,en.html  accessed 20-06-2020

4.  Lund J.W.,  D. H. Freeston., T. L. Boyd (2020) Direct Utilization of Geothermal Energy 2020 Worldwide Review, Proceedings World Geothermal Congress 2020

5.  Holmberg. H., O. K. Sønju., E. Næss (2020) A novel concept to engineered geothermal systems, Proceedings,  Thirty-Seventh Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California.

Solar panel and equipment warranties

Note: this is a revised re-post from my old defunct blog

A year ago I was using the Enlighten web interface for the microinverters on my solar array and noticed immediately that one of the solar panels was dropping out at different times of the day and producing only 1 or 2 Watts.  (Microinverters convert DC from the solar panel to 240 Volts AC that feeds into the building and electric grid).  The Enlighten user interface lets me replay the energy produced by my array throughout the day showing Watts produced per panel and the brightness of each panel representing relative power output.  This system granularity is a very helpful tool and is one of the best features of using micro-inverters because you can isolate and identify issues at specific panels very readily.

screen shot of Enlighten web portal

I emailed Enphase tech support and they responded by saying that they would try uploading new software to the microinverter behind that panel.  (Doesn't it blow you away that they can do that!).  A week later the panel dropped out completely and was no longer producing any power so I called tech support and talked to very helpful person who explained that they had tried the upload and it had not worked so they had already issued a replacement microinverter.  Apparently inverters tend to fail within the 1st 2 years of operation and it is unusual for one to fail after 4+ years.

Enphase inverters have a 15 year warranty and solar panels ALL come standard with 20-25 year warranties.  Once the replacement inverter arrived, it was a relatively simple matter to shut down the array and go up on a couple of ladders with my neighbor and remove the solar panel to access the inverter.  At which point it is largely plug and play to replace and then bolt down the new inverter and solar panel.  Here is then new microinverter:

And now I am back to normal again:  

The value of my solar power system is enhanced by excellent warranties and customer service.  I hope that by sharing this experience I will allay any concerns my readers may have about their potential investment in solar energy.

Safe disposal of unused medications

Last year I had to have emergency surgery and the hospital prescribed some opiate painkillers for my recovery.  I only took one or two of those pills because they made me feel so woozy, and the pain was quite tolerable with a little help from ibuprofen.  Recently I looked at that bottle of painkillers in my medicine cabinet and decided to dispose of it safely.  I am quite aware that there has been a significant increase in the abuse of opiates nationally and here in the state of Maine.  Apparently some house break-ins are now being attributed to drug addicts looking for opiates in medicine cabinets.  Medications are typically placed in the trash or dumped in the toilet, neither of these options are environmentally responsible.  In previous years, my wife and I would take our unused medications to an annual return drive at one of the local fire departments. 

Me disposing meds in the MedReturn box at our local police station

Last year there was a big push on a national level to make it easier for people to keep these dangerous narcotics and pharmaceuticals off the streets so now there are return boxes located in police and sheriffs departments throughout the country.  This makes it very easy and convenient to safely dispose of these potentially dangerous medications.  Here is a good article in the New York Times about the new return policy implemented by the DEA.  To locate a MedReturn drug collection box near you, you can go to their website: http://www.medreturn.com.  Medications are collected and responsibly disposed, typically by incineration.  They have a map you can use to search by ZIP Code and I found 5 drop-off sites within 10 miles of my home.

The other reason it is a good idea to dispose of these medications this way is to keep these chemicals out of the waste water treatment plants which cannot process them.  For instance, when birth control pills containing synthetic estrogen or other hormones enter the waste water stream they can have significant adverse effects on aquatic life. According to this NPR article, it has caused some species of male fish to become feminized, even causing them to produce eggs in their testes.  The issue can be severe enough to cause a collapse of an entire fish population resulting in near extinction.

From a sustainability standpoint is up to us to take full responsibility for all aspects of our waste, particularly to protect the environment from harmful side effects of these chemicals entering our streams, rivers and lakes.

Stemning fra en internasjonal konferanse

De siste dagene har det vært en stor, internasjonal elkraftkonferanse i Trondheim: PowerTech 2020. Det har stort sett vært deltagere fra alle verdens hjørner, som dekker de fleste underområder av fagområdet mitt, alt fra overordnede kraftmarkedsmodeller til detaljer på komponentnivå. Med dette mangfoldet fant jeg ut at det kunne være spennende å ta "tempen" litt på holdningen til fornybar energi, og da kanskje spesielt offshore vindkraft, og prøve å sammenligne litt med stemningen i Norge, for å se om det var noen veldig store forskjeller.

Vel, etter å ha vært på konferansen i fire dager er den spennende konklusjonen at det er ganske likt. Eller, dvs. vindkraft på land diskuteres bare i liten grad, og sjeldent ut i fra skal/skal ikke bygge ut prinsippet. Også er offshore vindkraft stort sett synonymt med bunnmonterte konstruksjoner. Og det er forbausende få som nevner det som etter hvert har blitt den store klisjeen her til lands: "Norge, Europas batteri". Skal vi bli det, så må vi tydeligvis markedsføre oss mer enn det som gjøres i dag.

I tillegg til de to store fornybare energikildene, i følge elkraftmiljøet, vind og sol, presenterte noen forskere fra Oregon state university et av sine mange bølgekraftverksprosjekter. Som mange andre løsninger virker det spennende, men etter å ha sett mange feilslåtte prosjekter, så er jeg bare betinget optimist.

Solar water heater benefits and ROI

Back in 2006 I decided to install solar collectors for the domestic hot water system in my home in Maine.  At a purchase price of around $3000, I calculated that it paid for itself within 4.6 years (after incentives) by reducing use of propane to heat domestic hot water by nearly 50%.  I did do some modifications of my own to improve performance and I expect to save well over $11,000 in propane costs over 25 years.  

I enlisted friends and neighbors to assist in the installation and it went quite well.  Just a few hours one afternoon to get the collectors mounted, and a few more afternoons to do all the interior wiring and plumbing.

I wrote a detailed blog about the installation on my website that details the entire process of installing this well-designed kit.  I purchased the kit from Butler Sun Solutions in California and could not be more pleased with everything they provided.  The system has required little to no maintenance and continues to perform extremely well.

The chart above shows two days worth of temperature readings for the collectors and storage tank from June 17 and 18, 2020.  Click on the image to see a live version of this chart on my website.  Because the collectors are mounted vertically to the south facing wall of my house, the performance is a little compromised during the summer when the sun is higher in the sky.  (Solar collectors for work best when they are pointed directly at the sun).  I get best performance in spring and fall when the sun angle is lower and the temperatures are moderate.  Water from our well comes into the house at approximately 55°F and temperatures in the storage tank can exceed 110°F after a good sunny day.  Performance is quite good in the winter depending on outside temperatures which remain below freezing for most of the winter here in Maine.  

Preheated water from the solar storage tank is fed directly into a propane tankless demand heater that I installed in 2010 to replace the old tank water heater that failed.  By feeding pre-warmed water into the demand heater I am dramatically reducing the amount of propane needed to bring the water up to temperature.


The image above diagrams the complete system and makes it look relatively simple.  If you are comfortable doing basic household plumbing and carpentry, then this DIY kit is an excellent choice as a retrofit to reduce the energy consumption in your home and I cannot recommend Butler Sun Solutions highly enough.

Quakers in Maine host a solar farm

I am a Quaker and was raised in England where the religion began.  We are properly called: "The Religious Society of Friends in Search of the Truth", or just Friends.  I am active member of the Midcoast Friends Meeting in rural Damariscotta, Maine and we recently decided to host a solar farm on our property.

The story begins in 2020 when Pope Francis released his encyclical entitled "Laudato Si".  The remarkable document is a call to action on climate change in which His Holiness lays out the issues clearly and concisely.  He talks knowledgeably about the science (he has a degree in science), but more importantly he chastises the world for placing capitalism ahead of the well being of humanity and all life on earth.  As he said once: “God always forgives; human beings sometimes forgive; but when nature is mistreated, she never forgives.” It is well worth reading and religious communities - Catholic and otherwise - have responded all over the world by taking action.  Some have divested their investments from fossil fuels, other have installed solar panels on their church roofs, and many other actions are being taken.

Friends found his message deeply moving and several of us formed a discussion group in late 2020 to explore his message and called it the "Climate Justice Group".  We met monthly and after talking about the encyclical for a while, we felt called to take action.

3 175W solar panels installed on Meeting House roof in 2008

Over the years we had already taken many steps to "green" the building by installing 3 solar panels on the roof (back when they were very pricey).  They offset a portion of the buildings needs. We also replaced all the lights with CFLs, and more recently LEDs as they burn out.  We switched the heating oil to a blend of bio-fuel and installed interior storm windows in the winter.  Many Friends drive hybrid or plug in hybrid vehicles and 3 of us have electric vehicles (Chevy Volts and Bolt).

We were aware of a solar farm that been installed nearby.  This consists of over 170 solar panels that produce up to 50kW.  9 co-op owners get to use that energy to offset their electric bill.  Each member purchases as many panels as they need to offset as much of their energy as they choose.  The co-op leases the land from a landowner with open property to spare.

After some discussion the Meeting approved the idea of hosting a solar farm on our property and approached ReVision Energy - the largest solar installer in Maine to let them know we had a site available.  ReVision staff were very enthusiastic and actively supported and promoted the solar farm.  By the winter of 2020 the farm was fully subscribed with 9 owners and we signed papers leasing the land at the bottom of our field.  The Meeting House will get over $600 per year for the lease.

On Thursday, June 22, 2020 I got approval to turn the whole solar farm on.  Here's a picture of me activating one of the 5 inverters:

The solar array was producing 44.6kW after it was all powered up!

Here is an article in the local paper about the farm in the local Lincoln County News.

A web page for the Midcoast Friends Community Solar Farm show performance metrics. 




Here are some images showing the ReVision Energy crew installing the equipment:

installing posts and racking

rails installed

sturdy steel post with aluminum brackets

half the panels installed

5 inverters and controls

completed Midcoast Friends Community Solar Farm

Utility connecting the farm to the grid

View from the Meeting House

A few Friends were dismayed by the impact of the sight lines as seen from the front porch of the building.  So we have planted 2 dozen shrubs and bushes along the back to form a screen so we won't see the less attractive back side of the solar array once they grow in.

planting miniature arbor vitae trees

Quakers have made this statement concerning our perspective:

"Our faith as Quakers is inseparable from our care for the health of our planet Earth. We see that our misuse of the Earth’s resources creates inequality, destroys community, affects health and well-being, leads to war and erodes our integrity. We are all responsible for stewardship of our natural world. We love this world as God’s gift to us all. Our hearts are crying for our beloved mother Earth, who is sick and in need of our care."

For the whole document, click below:

Living Sustainably and Sustaining Life on Earth – The Minute from the Plenary
February 20, 2020

Hopefully our small contribution in support of renewable energy will help slow the impact of climate change.

Noreg - ein framtidig biogassnasjon?

 

Av Kristian Fjørtoft, stipendiat ved Institutt for matematiske realfag og teknologi (IMT), Universitet for Miljø og Biovitenskap (UMB)

Svar: Nei!

Det er lite truleg at biogass , i overskodeleg framtid, vil utgjere ein betydeleg del av BNP i Noreg. Like  vel kan biogass utgjere ein særs verdifull del av det framtidige biletet der fornybar energi skal dekkje ein stadig større del av Noreg sitt energibehov.

I arbeidet mitt her ved UMB har eg mellom anna sett på sett på forbehandling av halm og samrotning av storfegjødsel med ulike tilleggssubstrat. Det er eigentleg ganske utruleg at mikroorganismar dannar høgverdig kjemisk energi frå avfall og gjødsel. I følgje Raadal et.al. (2020) kan avfall og biprodukt på landsbasis gje seks TWh i året i form av biogass. Etter utrotninga vil substratet ved eit gardsbiogassanlegg verte nytta til gjødsel på åker til ny fôr- og matproduksjon. Næringsemna har gjennom prosessen ikkje berre vorte bevart men også gjort meir plantetilgjengeleg. Såleis styrker ein grunnlaget for matproduksjon for komande generasjonar samstundes som ein hentar ut fornybar energi.

Frå ein kubikkmeter med flytande storfegjødsel har vi i forsøk fått over 90 kWh energi i form av metan, medan frå matavfall har vi fått over 900 kWh per kubikkmeter. Biogassproduksjonen vil variere etter innhald av organisk tørrstoff i substrata, samt kor lett dei let seg bryte ned. Det å flytte store mengder gjødsel til sentrale anlegg, vil truleg påvirke den totale energibalansen negativt. I Sverige og Danmark har ein no byrja å sjå på konsept der ein har biogassanlegg ute på dei enkelte gardsbruka og i staden sender gassen gjennom røyr til sentral oppgradering. Matavfallet vert i dag til ei viss grad nytta til produksjon av biogass ved sentrale anlegg. Ein del vert til dømes skipa til biogassanlegg i Danmark. Matavfall og andre energirike tilleggssubstrat bør heller nyttast ved norske anlegg, og slik styrke den nasjonale produksjonen av fornybar energi. Det å bruke fossil energi på å transporterer energi og næringsstoff ut av landet er svært lite framtidsretta.

Biogass består av om lag 60 prosent metan. Etter ei enkel oppgradering kan difor biogass erstatte naturgass. LBG (Liquid biogas) vil såleis kunne erstatte LNG (Liquid natural gas) og vere eit godt alternativ for skip og langtransport etter veg, medan CBG (Compressed biogas) vil kunne erstatte CNG (Compressed natural gas) og vere drivstoff for bussar og personbilar med lang rekkevidde. Av metan frå biogass kan ein også syntetisk lage metanol, som via produksjon av formaldehyd kan verte nytta i produksjon av plastikk og måling. Metanol kan også verte nytta i produksjonen av biodiesel. Viktigaste bruksområdet vil truleg like vel vere å nytte metanen til drivstoff.

Biogass vil såleis kunne vere ein viktig del av det framtidige energibiletet både i Noreg og internasjonalt.

Referansar:

Raadal, H. L., Schakenda, V., Morken, J., 2020. Potensialstudie for biogass i Norge. Rapport . Østfoldforskning og Universitetet for miljø og biovitenskap.